Port to Minecraft 1.21.11

Port to Minecraft 1.21.8. Code changes are relatively minor, but please report any issues you encounter.

Port to Minecraft 1.21.5. Once again, this includes significant changes. Please report any issues you encounter.

Port to Minecraft 1.21.4. This includes some significant changes. Please don't hesitate to report any issues.

Port to Minecraft 1.21.3. This includes significant rewrites of multiple systems. Please don't hesitate to report any issues.