MM-52532: Fix golangci warnings (#23709)

https://mattermost.atlassian.net/browse/MM-52532

- Replace golint with revive
- Add makezero linter
- Fix all the required linter failures

Some issues in enterprise and public modules
are yet to be fixed. We send this to expediate things.

server/public/model/channel_data.go

@@ -9,7 +9,7 @@ type ChannelData struct {
 }
 
 func (o *ChannelData) Etag() string {
-	var mt int64 = 0
+	var mt int64
 	if o.Member != nil {
 		mt = o.Member.LastUpdateAt
 	}