Bug 17661: (follow-up) Update regex to support Unicode characters

Bug 17661: (follow-up) Update regex to support Unicode characters

Rather than limiting initials to [A-Z] we should test for a broad
range of uppercase letters.

The ES/Zebra changes are slightly different because of Perl vs Java regex
conventions. POerl may support either, but I found 'Uppercase' to be a bit more explicit

More info here:
https://perldoc.perl.org/perlunicode.html

TO test:
Same plan as before but use Ж. as the ending initial
Confirm the period is preserved and other punctuation removed

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>