.NET: `\p{LC}` doesn't work, `.` and `\w` doesn't properly support Unicode

[Aloso]

All identified problems (most have been addressed in Pomsky 0.10):

• [x] .NET doesn't support code points (in hexadecimal notation) outside the BMP – must be converted to two UTF-16 surrogates
  • [x] make it work in string literals (e.g. '𐌰')
  • [x] make it work for hexadecimal code points above U+FFFF (e.g. U+10330) instead of producing an error
• [ ] #89
• [x] \pL as shorthand for \p{L} doesn't work
• [x] \p{LC} doesn't work
  • [ ] polyfill?
• [x] scripts and boolean properties don't work at all
• [x] needs investigation to see if all blocks are supported
• [x] check if block names are correctly normalized: underscores must be removed, but dashes preserved
• [x] \v and \h aren't supported
• [ ] #88
• [x] need to check if backreferences like \80 are too high (doc)
• [x] any further bugs may surface during fuzzing

To Reproduce

The regex-test crate ~~should be~~ was expanded to run .NET tests and run in CI (currently only on Ubuntu).

Expected behavior

.NET flavor works reliably, using unsupported features produces an error.