[meta] Update database-centric libraries

[miketheman]

We've got newer libraries to look at for database accesses, and need a sane workflow to get us to the finish line.

Here's an outline of execution:

• [x] Upgrade to latest SQLAlchemy 1.4.x - done - we're on 1.14.47
• [x] Run tests with SQLALCHEMY_WARN_20=1 to surface all Deprecation warnings, resolve those post-haste
  • [x] #13511
  • [x] #13784
  • [x] #13785
  • [x] #13845
  • [x] #13895
• [x] Set future=True on sessionmaker & create_engine and run tests
  • [x] Fails on session passing in Event.ip_address magic, which we should probably remove after every Event has a related IPAddress (see #13804 #13823 #13842)
  • [x] Fails on test case. Refactor: #13889
• [x] Upgrade to SQLalchemy 2.0.16 https://github.com/pypi/warehouse/pull/13929
  • [x] #13942
  • [x] Read https://docs.sqlalchemy.org/en/20/changelog/migration_20.html
  • [x] Replace sqlalchemy-citext as it's no longer needed, there's a built-in https://docs.sqlalchemy.org/en/20/dialects/postgresql.html#sqlalchemy.dialects.postgresql.CITEXT
  • [x] #13948
  • [x] #13950
• [x] Upgrade psycopg3 - see https://github.com/pypi/warehouse/pull/10742
• [x] Upgrade pytest-postgresql to 5.x
• [x] Celebrate!

[miketheman]

As of today, we've updated all the libraries and associated code to make them work.

There's still outstanding work to convert to SQLAlchemy 2.0 ORM PEP-484 support, but that can be completed outside this work.

Major kudos to @di, @ewdurbin , @dstufft for all their work on making this happen!