v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/channels/app/worktemplates/generator/main.go

@@ -19,7 +19,7 @@ import (
 	"golang.org/x/tools/imports"
 	"gopkg.in/yaml.v3"
 
-	"github.com/mattermost/mattermost-server/v6/server/channels/app/worktemplates"
+	"github.com/mattermost/mattermost-server/server/v8/channels/app/worktemplates"
 )
 
 type WorkTemplateWithMD5 struct {

server/channels/app/worktemplates/model.go

@@ -6,9 +6,9 @@ import (
 	"errors"
 	"net/http"
 
-	pbclient "github.com/mattermost/mattermost-server/v6/server/playbooks/client"
+	pbclient "github.com/mattermost/mattermost-server/server/v8/playbooks/client"
 
-	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/server/v8/model"
 )
 
 type ExecutionRequest struct {

server/channels/app/worktemplates/model_test.go

@@ -8,9 +8,9 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/server/v8/model"
 
-	pbclient "github.com/mattermost/mattermost-server/v6/server/playbooks/client"
+	pbclient "github.com/mattermost/mattermost-server/server/v8/playbooks/client"
 )
 
 func TestCanBeExecuted(t *testing.T) {

server/channels/app/worktemplates/types.go

@@ -8,8 +8,8 @@ import (
 
 	"github.com/pkg/errors"
 
-	"github.com/mattermost/mattermost-server/v6/model"
-	"github.com/mattermost/mattermost-server/v6/server/platform/shared/i18n"
+	"github.com/mattermost/mattermost-server/server/v8/model"
+	"github.com/mattermost/mattermost-server/server/v8/platform/shared/i18n"
 )
 
 type WorkTemplateCategory struct {