Fully parallel menu world building

[Techjar]

No more game freeze or lag while building the geometry. There may be some slight stutters caused by the GC if the heap isn't super large, due to the huge amount of garbage generated. I also made the download and file read async.

Needs testing on:

• [x] OptiFine
• [x] OptiFine with Shaders
• [x] Iris Shaders
• [x] Possibly other things that affect the renderer

[Techjar]

Is there any other cases that need to be tested?

[fayer3]

I checked nvidium, which messes with the chunk building, and that worked fine

[fayer3]

I can check canvas, but not sure if that even worked before

[Techjar]

Sounds good to me then. As before, there's enough exception checks that it at least shouldn't crash the game in whatever edge cases are hit in production.