Fix. Leave group actions (#1774)

Fix for issue #1768 where the bot master was not getting reset. 
I also cleaned up leave group action to focus up function scope.
I moved the resets from #612 to the actual leaving function.

Disclosure: LLMs were NOT used in authoring this PR.

Test cases to consider for testers.
1. Master disbands group with random bots. Bots should go about their
business.
2. If you can dual box, create a raid where two real player both invite
random bots. One player leaves group, their bots should also leave.
(edge case, if a random bot that is supposed to leave the group becomes
leader they may disband the whole group.

src/PlayerbotAI.h

@@ -529,7 +529,8 @@ public:
 
     Player* GetBot() { return bot; }
     Player* GetMaster() { return master; }
-
+    Player* FindNewMaster();
+    
     // Checks if the bot is really a player. Players always have themselves as master.
     bool IsRealPlayer() { return master ? (master == bot) : false; }
     // Bot has a master that is a player.
@@ -611,7 +612,7 @@ private:
     static void _fillGearScoreData(Player* player, Item* item, std::vector<uint32>* gearScore, uint32& twoHandScore,
                                    bool mixed = false);
     bool IsTellAllowed(PlayerbotSecurityLevel securityLevel = PLAYERBOT_SECURITY_ALLOW_ALL);
-    void UpdateAIGroupMembership();
+    void UpdateAIGroupAndMaster();
     Item* FindItemInInventory(std::function<bool(ItemTemplate const*)> checkItem) const;
     void HandleCommands();
     void HandleCommand(uint32 type, const std::string& text, Player& fromPlayer, const uint32 lang = LANG_UNIVERSAL);