feat: add WithWorldGuard and HandlerContext system parameters

[makspll]

This should allow things like:

fn my_system(mut with_guard: WIthWorldGuard<HandlerContext<LuaScriptingPlugin>>) {
	let (world_guard, handler_ctxt) = with_guard.get_mut();
	handler_ctxt.call("my_script" , ... // etc )
}

In theory it also lets you call scripts in ANY system, however the world guard will know about the other resources/ components being accessed, meaning that it will not be possible to access &mut from scripts if you access ANYTHING else (other than the handler context).

This is a good first step towards #244 , as it demonstrates how systems and WorldGuard should interact