Replace classes with pytest in test_sql (pandas-dev#55074)

* initial working test

* passing mixing class removal

* converted non-sqlalchemy tests

* large refactor

* sqlite class conversion

* checkpoint

* sqlitefallback conversion

* fixup tests

* no more test classes

* factory func

* most code cleanups

* removed breakpoint; passing tests

* fixes

* fix when missing SQLAlchemy

* more fixups when no SQLAlchemy

* fixups

* xfail -> skip

* sqlite fixture use transaction for cleanup

* verbose test for hangs

* try skipping sqlite-sqlalchemy-memory on rollback test

* sqlite sqlaclchemy memory cleanup

* revert verbose logging in tests

* mark all db tests

* try single_cpu

* skip more engine tests that can hang

* try no pandasSQL without transaction

* more skip

* try verbose

* transaction skips

* remove verbose CI

* CI verbose

* no more hanging

* reverted CI files

* type ignore

* cleanup skips

* remove marks

* mark fixtures

* mark postgres fixtures