Create a filesystem abstraction layer for CSM and only allow accessing files that are scanned into it. (#5965)

* Load client-side mods into memory before executing them.

This removes the remaining filesystem access that client-sided mods had and it will hopefully make then more secure.

* Lua Virtual filesystem: don't load the files into memory just scan the filenames into memory.

* Fix the issues with backtrace

* fix most of the issues

* fix code style.

* add a comment

src/script/lua_api/l_client.h

@@ -95,6 +95,9 @@ private:
 	// get_privilege_list()
 	static int l_get_privilege_list(lua_State *L);
 
+	// get_builtin_path()
+	static int l_get_builtin_path(lua_State *L);
+
 public:
 	static void Initialize(lua_State *L, int top);
 };