Core/Game: Include cleanup

* Mostly aimed at removing Log/DatabaseEnv includes from other headers
* Fix most packet headers including other packet headers - moved common structures such as ItemInstance to their own files
* Moved SAI function definitions to source files (massive or requiring many different dependencies)

src/server/game/Handlers/AuthHandler.cpp

@@ -21,7 +21,10 @@
 #include "CharacterTemplateDataStore.h"
 #include "ClientConfigPackets.h"
 #include "ObjectMgr.h"
+#include "RBAC.h"
+#include "Realm.h"
 #include "SystemPackets.h"
+#include "World.h"
 
 void WorldSession::SendAuthResponse(uint32 code, bool queued, uint32 queuePos)
 {