Implement the Kitty Keyboard Protocol (microsoft#19817) (#10)

This essentially rewrites `TerminalInput` from scratch.
There's significant overlap between what kind of information
the Kitty protocol needs from the OS and our existing code.
The rewrite allows us to share large parts of the implementation.

Closes microsoft#11509

## Validation Steps Performed
* `kitten show-key -m kitty` ✅
* US Intern. " + ' produces `\'` ✅
* Hebrew base keys produce Unicode ✅
* Hebrew AltGr combinations produce Unicode ✅
* French AltGr+Space produces U+00A0 ✅
* German AltGr+Decimals produce []{}... ✅

Co-authored-by: Leonard Hecker <[email protected]>

Author: Dargon789