MixinChunkRebuildTask

Implements the main hooks for terrain rendering. Attempts to tread lightly. This means we are deliberately stepping over some minor optimization opportunities.

Non-Fabric renderer implementations that are looking to maximize performance will likely take a much more aggressive approach. For that reason, mod authors who want compatibility with advanced renderers will do well to steer clear of chunk rebuild hooks unless they are creating a renderer.

These hooks are intended only for the Fabric default renderer and aren't expected to be present when a different renderer is being used. Renderer authors are responsible for creating the hooks they need. (Though they can use these as an example if they wish.)