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/platform/services/cache/mocks/Provider.go

@@ -5,7 +5,7 @@ package mocks
 import (
 	mock "github.com/stretchr/testify/mock"
 
-	cache "github.com/mattermost/mattermost-server/v6/server/platform/services/cache"
+	cache "github.com/mattermost/mattermost-server/server/v8/platform/services/cache"
 )
 
 // Provider is an autogenerated mock type for the Provider type