⚡✅ Update Stringprep BIDI regexps to run in O(n)

The BIDI_FAILURE regexps all used `\g<name>` to define char classes and
then re-use them.  Unfortunately, ruby 3.2 can't compile that to run in
linear time.  The regexps could also be written using lookahead, but
that also wouldn't run in linear time.

Author: nevans