Global hook features and improvements, ExecuteInGameThread helper

[wildcherry2]

I'm really liking this tool so far, I used to use/make similar tools for UE3 games and this whole project probably has more effort put into it than any of those tools. But there are a few things I noticed or think could be improved:

1. Global hooks (in hooks.cpp ) aren't thread safe, which is a problem for more complicated mods that take advantage of multithreading or do more work in the ImGui thread, or otherwise only conditionally hook into those functions. I think there's already a PR that adds basic thread safety in the UEPseudo repo, it just needs to be accepted, see the PR
2. Global hooks can't be removed like per-function hooks can. Again, this is an issue for more complicated mods that conditionally hook those functions.
3. It can be ambiguous to determine which thread C++ mods are running in. I've noticed in the ctor, its running in the game thread, but in the on_unreal_init function, its running on a different thread, which also makes me wonder how accessing Unreal:: things are safe if it's not in the game thread. Note that I tested this by hooking the engine's, actor's, and viewport's tick method and comparing thread IDs with code running in on_unreal_init, so unless I'm misunderstanding something or there's some thread-safe guarantee I'm missing, accessing Unreal:: things may not actually be safe in the on_unreal_init function. I think that there should be some static globals that hold the thread IDs of useful/known threads, then modders can add asserts to ensure code is running on the right thread.
4. There needs to be a helper for executing callbacks in the game thread. It can be implemented with a hook into the engine's/viewport's tick function that drains a thread-safe queue of callbacks.

I can start implementing these ideas if you'd like, but I want to make sure these are good/useful ideas and that I'm not just missing some part of the API that already does these things or doing something that's already being worked on. Thanks!