MM-12849 Moving all non request scoped items to Server struct (#9806)

* Moving goroutine pool

* Auto refactor

* Moving plugins.

* Auto refactor

* Moving fields to server

* Auto refactor

* Removing siteurl duplication.

* Moving reset of app fields

* Auto refactor

* Formatting

* Moving niling of Server to after last use

* Fixing unit tests.

app/reaction.go

@@ -42,7 +42,7 @@ func (a *App) SaveReactionForPost(reaction *model.Reaction) (*model.Reaction, *m
 
 	reaction = result.Data.(*model.Reaction)
 
-	a.Go(func() {
+	a.Srv.Go(func() {
 		a.sendReactionEvent(model.WEBSOCKET_EVENT_REACTION_ADDED, reaction, post, true)
 	})
 
@@ -92,7 +92,7 @@ func (a *App) DeleteReactionForPost(reaction *model.Reaction) *model.AppError {
 		return result.Err
 	}
 
-	a.Go(func() {
+	a.Srv.Go(func() {
 		a.sendReactionEvent(model.WEBSOCKET_EVENT_REACTION_REMOVED, reaction, post, hasReactions)
 	})