Expand and improve electric-pair-mode and Python testing (bug#49518)

Expand and improve electric-pair-mode and Python testing (bug#49518)

In python-tests.el, the triple-quote pairing tests are passing
incorrectly, i.e. the auto-pairing functionality they purport to guard
isn't really working for users trying it interactively.  Added a new
failing test, soon to be fixed.

In electric-tests.el, added tests for Python, too.

* test/lisp/electric-tests.el (define-electric-pair-test): Also run
main tests for python-mode.  (pair-some-quotes-skip-others): Test
another slightly different pairing.

* test/lisp/progmodes/python-tests.el
(python-triple-double-quote-pairing): Rename from
python-triple-quote-pairing.
(python-triple-single-quote-pairing): New test.