Playable on 1-21-rc7 at the time of writing

1-21-rc Update to playable state on 1.21-rc7 at the time of writing

More specifically:
- Bump .NET version 7.0 -> 8.0
- Increase minor version component by 1 inside modinfo.json
- Adapt Block.OnEntityCollide Harmony Prefix to not use `.minHorRangeToClient` which doesn't seem to exist anymore
  - instead, try and check if any online players are within the entity's range