CharInfo: implement C23 rules for identifiers

[ehaas]

This is the first part of the c23 unicode update; the second part will be adding identifier normalization.

[Vexu]

the second part will be adding identifier normalization.

There might already be a Zig library for this that we could use.

[ehaas]

It looks like maybe we can get away with just rejecting non-normalized identifiers?

https://open-std.org/JTC1/SC22/WG14/www/docs/n2836.pdf

Therefore, normalization of identifiers must happen before object files are emitted. It is either the
responsibility of programmers to provide normalized identifiers, and compilers to either warn or error
on non-normalized ones, or for compilers to normalize Unicode input. For non-Unicode input, the
transformation to normalized form is the simple table based lookup used to translate now.

This project provides code that handles the normalization form we'll need https://codeberg.org/dude_the_builder/ziglyph

[Vexu]

It looks like maybe we can get away with just rejecting non-normalized identifiers

That would be nice. We should definitely detect non-normalized identifiers since there is a simple check for it and the tables for NFC_Quick_Check={No,Maybe} are quite small.