Get rid of not implemented SESSION_GTIDS_TRACKER

One less new/delete per connection.

Part of MDEV-14984 - regression in connect performance

sql/session_tracker.cc

@@ -34,20 +34,6 @@ void State_tracker::mark_as_changed(THD *thd, LEX_CSTRING *tracked_item_name)
 }
 
 
-class Not_implemented_tracker : public State_tracker
-{
-public:
-  bool enable(THD *thd)
-  { return false; }
-  bool update(THD *, set_var *)
-  { return false; }
-  bool store(THD *, String *)
-  { return false; }
-  void mark_as_changed(THD *, LEX_CSTRING *tracked_item_name)
-  {}
-
-};
-
 /**
   Session_sysvars_tracker
 
@@ -1443,8 +1429,6 @@ void Session_tracker::enable(THD *thd)
     new (std::nothrow) Current_schema_tracker;
   m_trackers[SESSION_STATE_CHANGE_TRACKER]=
     new (std::nothrow) Session_state_change_tracker;
-  m_trackers[SESSION_GTIDS_TRACKER]=
-    new (std::nothrow) Not_implemented_tracker;
   m_trackers[TRANSACTION_INFO_TRACKER]=
     new (std::nothrow) Transaction_state_tracker;
 

sql/session_tracker.h

@@ -32,7 +32,6 @@ enum enum_session_tracker
   SESSION_SYSVARS_TRACKER,                       /* Session system variables */
   CURRENT_SCHEMA_TRACKER,                        /* Current schema */
   SESSION_STATE_CHANGE_TRACKER,
-  SESSION_GTIDS_TRACKER,                         /* Tracks GTIDs */
   TRANSACTION_INFO_TRACKER,                      /* Transaction state */
   SESSION_TRACKER_END                            /* must be the last */
 };