Properly indent Python PEP634 match/case blocks

Properly indent Python PEP634 match/case blocks

Python 3.10 introduced the "structural pattern matching" syntax, and
commit 139042eb8629e6fd49b2c3002a8fc4d1aabd174d told font-lock about the
new keywords. This adds them also as block-start statements, to enable
proper indentation of such blocks.

* lisp/progmodes/python.el (python-rx): Add "match" and "case" as
block-start keywords.
* test/lisp/progmodes/python-tests.el (python-indent-after-match-block,
python-indent-after-case-block): New tests to verify indentation of
"match" and "case" blocks (bug#55572).