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/Scripting/ScriptSystem.h

@@ -19,8 +19,11 @@
 #ifndef SC_SYSTEM_H
 #define SC_SYSTEM_H
 
-#include "ScriptMgr.h"
+#include "Define.h"
+#include "Hash.h"
 #include "SplineChain.h"
+#include <unordered_map>
+#include <vector>
 
 class Creature;