Mostly in prep for 1.19.4.
- Update to Loom 1.1.
- Simplifies our handling of remapped configurations a little.
- Removes the need for a fake fabric.mod.json in the API jar.
For reasons I don't quite understand, this required us to bump the
Fabric API version. Otherwise interfaces are not injected.
- Update to Rollup 3.0.
- Do NOT update NullAway: It now correctly checks @Nullable fields in
inherited classes. This is good, but also a pain as Minecraft is a
little over-eager in where it puts @Nullable.