Parallel resource loading

[adriengivry]

Problem this feature should fix
Some scenes take a long time to load

Expected solution
Loading resources in parallel, on multiple threads, could vastly speed up scene loading. Some resources need to interact with the OpenGL context, which is mono-threaded, therefor, loading should be split in 2 methods: CPU-side (can be parallelized), GPU-side (needs synchronization with main thread). When attempting to load a scene, we should resolve all the resource that will be needed, and batch load them.

[SerenityCodes]

If no one is already working on this, I'll take this issue

[adriengivry]

@SerenityCodes no one is working on it at the moment, so feel free!!

[SerenityCodes]

Great! I'll get working on this