* Fixed unions of `nil` types displaying as `?`
* Internal normalization now handles class types which can make
previously failing (incorrectly) sub-typing checks to succeed
- Remove type definitions of
`utf8.nfcnormalize`/`nfdnormalize`/`graphemes` that aren't supported by
standalone Luau library
- Add `lua_costatus` to retrieve extended thread status (similar to
`coroutine.status`)
- Improve GC sweeping performance (2-10% improvement on allocation-heavy
benchmarks)