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
```

store/searchlayer/channel_layer.go

@@ -8,10 +8,10 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/store"
 )
 
 type SearchChannelStore struct {

store/searchlayer/file_info_layer.go

@@ -4,10 +4,10 @@
 package searchlayer
 
 import (
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/store"
 )
 
 type SearchFileInfoStore struct {

store/searchlayer/layer.go

@@ -7,10 +7,10 @@ import (
 	"context"
 	"sync/atomic"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/store"
 )
 
 type SearchStore struct {

store/searchlayer/layer_test.go

@@ -8,12 +8,12 @@ import (
 	"sync"
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/store/searchlayer"
-	"github.com/mattermost/mattermost-server/v5/store/sqlstore"
-	"github.com/mattermost/mattermost-server/v5/store/storetest"
-	"github.com/mattermost/mattermost-server/v5/testlib"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/store/searchlayer"
+	"github.com/mattermost/mattermost-server/v6/store/sqlstore"
+	"github.com/mattermost/mattermost-server/v6/store/storetest"
+	"github.com/mattermost/mattermost-server/v6/testlib"
 )
 
 // Test to verify race condition on UpdateConfig. The test must run with -race flag in order to verify

store/searchlayer/post_layer.go

@@ -8,10 +8,10 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/store"
 )
 
 type SearchPostStore struct {

store/searchlayer/team_layer.go

@@ -4,8 +4,8 @@
 package searchlayer
 
 import (
-	model "github.com/mattermost/mattermost-server/v5/model"
-	store "github.com/mattermost/mattermost-server/v5/store"
+	model "github.com/mattermost/mattermost-server/v6/model"
+	store "github.com/mattermost/mattermost-server/v6/store"
 )
 
 type SearchTeamStore struct {

store/searchlayer/user_layer.go

@@ -9,10 +9,10 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/mattermost/mattermost-server/v5/model"
-	"github.com/mattermost/mattermost-server/v5/services/searchengine"
-	"github.com/mattermost/mattermost-server/v5/shared/mlog"
-	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/services/searchengine"
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/mattermost/mattermost-server/v6/store"
 )
 
 type SearchUserStore struct {