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/HotfixHandler.cpp

@@ -20,6 +20,7 @@
 #include "DB2Stores.h"
 #include "HotfixPackets.h"
 #include "Log.h"
+#include "World.h"
 
 void WorldSession::HandleDBQueryBulk(WorldPackets::Hotfix::DBQueryBulk& dbQuery)
 {