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/api4/resolver.go

@@ -10,10 +10,10 @@ import (
 
 	"github.com/graph-gophers/dataloader/v6"
 
-	"github.com/mattermost/mattermost-server/v6/model"
-	"github.com/mattermost/mattermost-server/v6/server/channels/app"
-	"github.com/mattermost/mattermost-server/v6/server/channels/store"
-	"github.com/mattermost/mattermost-server/v6/server/channels/web"
+	"github.com/mattermost/mattermost-server/server/v8/channels/app"
+	"github.com/mattermost/mattermost-server/server/v8/channels/store"
+	"github.com/mattermost/mattermost-server/server/v8/channels/web"
+	"github.com/mattermost/mattermost-server/server/v8/model"
 )
 
 // cursorPrefix is used to categorize objects