Fixes & Improvements

Closes #4392, #4375, #4351, and #4444

See merge request !11273

Pit fight rework

See merge request !11265

Bodyswap cleanup

Closes #3040 and #4359

See merge request !11272

1. `$swappingSlave` is now an ID instead of a cloned object.
2. Eliminate many direct slave index lookups.
3. Clearly comment that `origBodyOwner` and `origBodyOwnerID` actually store exactly opposite data despite having pretty much the same name.
4. Fix various bugs dealing with tracking original bodies.
5. Fix body swap reactions upon regaining one's original body, and don't emit the same spuriously.

Apply tryKnockMeUP() to PC overhaul areas p1

See merge request !11270

Fixes

Closes #4479, #4472, and #4460

See merge request !11271