Pull in unicode_names as an internal crate

[antifuchs]

We appear to be dependent on a very recent unicode_names (or at least a synced-up one). Since that hasn't updated since unicode 8 (and that took a year), maybe we could pull in a slimmed-down version of https://github.com/ProgVal/unicode_names2 and release that as a workspace crate. It does use the same data file as we do, after all!

Maybe the same might apply to the unicode-width crate too, but it's less noticeable for my use case. Let's try unicode_names first.

[antifuchs]

Since we're now using unicode_names2 & I have commit access to that crate, the problem is pretty much resolved!