Performance improvements for 40M posts (#7708)

* Optimizing get root posts SQL query

* Setting session invalidation to be reliable

* Adding app reciever to SessionHasPermissionToUser

* Adding app reciever to SessionHasPermissionToTeam

* Adding app reciever to SessionHasPermissionTo

* Clear session cache if permission was denied

* Fixing rebase issues

* Revert "Optimizing get root posts SQL query"

This reverts commit f364757e7015cfb4ec673d0a4fc3d57cd25d8dd7.

* Fixing build

api/emoji.go

@@ -148,7 +148,7 @@ func deleteEmoji(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if c.Session.UserId != emoji.CreatorId && !app.SessionHasPermissionTo(c.Session, model.PERMISSION_MANAGE_SYSTEM) {
+	if c.Session.UserId != emoji.CreatorId && !c.App.SessionHasPermissionTo(c.Session, model.PERMISSION_MANAGE_SYSTEM) {
 		c.Err = model.NewAppError("deleteEmoji", "api.emoji.delete.permissions.app_error", nil, "user_id="+c.Session.UserId, http.StatusUnauthorized)
 		return
 	}