gh-94675: Add a regression test for rjsmin re slowdown (GH-94685)

Adds a regression test for an re slowdown observed by rjsmin.
Uses multiprocessing to kill the test after SHORT_TIMEOUT.

Co-authored-by: Oleg Iarygin <dralife@yandex.ru>
Co-authored-by: Christian Heimes <christian@python.org>
(cherry picked from commit fe23c0061d9c72527ad57a8c965d8161b00f500e)

Co-authored-by: Miro Hrončok <miro@hroncok.cz>