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/sharedchannel/mock_ServerIface_test.go

@@ -5,14 +5,14 @@
 package sharedchannel
 
 import (
-	mlog "github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+	mlog "github.com/mattermost/mattermost-server/server/v8/platform/shared/mlog"
 	mock "github.com/stretchr/testify/mock"
 
-	model "github.com/mattermost/mattermost-server/v6/model"
+	model "github.com/mattermost/mattermost-server/server/v8/model"
 
-	remotecluster "github.com/mattermost/mattermost-server/v6/server/platform/services/remotecluster"
+	remotecluster "github.com/mattermost/mattermost-server/server/v8/platform/services/remotecluster"
 
-	store "github.com/mattermost/mattermost-server/v6/server/channels/store"
+	store "github.com/mattermost/mattermost-server/server/v8/channels/store"
 )
 
 // MockServerIface is an autogenerated mock type for the ServerIface type