Capture group names were extended in

https://github.com/tc39/ecma262/pull/1869/files
https://github.com/tc39/ecma262/pull/1932/files

RegExpIdentifierName now explicitly enables unicode (+U) for
unicode escape sequences; likewise, surrogate pairs are now allowed
unconditionally.

The implementation simply switches on unicode temporarily while
parsing a capture group name.

Good news everyone, /(?<𝒜>.)/ is now a legal pattern.

Bug: v8:10384
Change-Id: Ida805998eb91ed717b2e05d81d52c1ed61104e3f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3233234
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77722}