MM-36271: Bump major version to 6.0 (#17973)

https://mattermost.atlassian.net/browse/MM-36271

```release-note
We bump the major version to 6.0
```

app/plugin_api_tests/manual.test_http_hijack_plugin/main.go

@@ -6,7 +6,7 @@ package main
 import (
 	"net/http"
 
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type Plugin struct {

app/plugin_api_tests/manual.test_http_upgrade_websocket_plugin/main.go

@@ -9,8 +9,8 @@ import (
 
 	"github.com/gorilla/websocket"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type Plugin struct {

app/plugin_api_tests/manual.test_load_configuration_defaults_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type configuration struct {

app/plugin_api_tests/manual.test_load_configuration_plugin/main.go

@@ -6,9 +6,9 @@ package main
 import (
 	"fmt"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type configuration struct {

app/plugin_api_tests/test_bots_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_call_log_api_plugin/main.go

@@ -6,8 +6,8 @@ package main
 import (
 	"github.com/pkg/errors"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type PluginUsingLogAPI struct {

app/plugin_api_tests/test_db_driver/main.go

@@ -7,12 +7,12 @@ import (
 	"database/sql"
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
-	"github.com/mattermost/mattermost-server/v5/shared/driver"
-	"github.com/mattermost/mattermost-server/v5/store/sqlstore"
-	"github.com/mattermost/mattermost-server/v5/store/storetest"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
+	"github.com/mattermost/mattermost-server/v6/shared/driver"
+	"github.com/mattermost/mattermost-server/v6/store/sqlstore"
+	"github.com/mattermost/mattermost-server/v6/store/storetest"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_get_bundle_path_plugin/main.go

@@ -7,9 +7,9 @@ import (
 	"fmt"
 	"path/filepath"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_get_channels_for_team_for_user_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_get_direct_channel_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_get_plugin_status_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_get_profile_image_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_member_channels_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_members_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_search_channels_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_search_posts_in_team_plugin/main.go

@@ -6,9 +6,9 @@ package main
 import (
 	"fmt"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_search_teams_plugin/main.go

@@ -6,9 +6,9 @@ package main
 import (
 	"fmt"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_send_mail_plugin/main.go

@@ -7,10 +7,10 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
-	"github.com/mattermost/mattermost-server/v5/shared/mail"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
+	"github.com/mattermost/mattermost-server/v6/shared/mail"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_set_profile_image_plugin/main.go

@@ -10,9 +10,9 @@ import (
 	"image/color"
 	"image/png"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_update_user_active_plugin/main.go

@@ -4,9 +4,9 @@
 package main
 
 import (
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {

app/plugin_api_tests/test_update_user_status_plugin/main.go

@@ -6,9 +6,9 @@ package main
 import (
 	"fmt"
 
-	"github.com/mattermost/mattermost-server/v5/app/plugin_api_tests"
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/plugin"
+	"github.com/mattermost/mattermost-server/v6/app/plugin_api_tests"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/plugin"
 )
 
 type MyPlugin struct {