Use SDL3's Storage API for Save Data?

[NoelFB]

I'm not sure about this yet, but SDL3 introduced a new Storage API that would be good for Save Data across platforms (desktop, consoles, web, etc). It may make sense to modify our UserStorage to use this as the backing implementation.

https://wiki.libsdl.org/SDL3/CategoryStorage

[NoelFB]

I partially implemented this in the SDL3/GPU branch here: fd83d4b

However there are some bugs with SDL that make this a bit hacky/unstable right now, particularly around their SDL_GlobStorageDirectory method which returns full paths, instead of virtual relative paths. I've hacked around it for now but I need to look into either fixing this in SDL or waiting for it to be resolved.

The other caveat is the SDL storage API requires you to wait for it to be ready (and not spinlock wait on the main thread), so I've implemented a wrapper around that before returning the actual Storage object to the user ... I think that's the easiest solution.