Test suite maintainence and new ideas #4324

Our test suite has once again degraded in performance and flakiness has been reintroduced. We can experiment / make our test suite better in different ways, some of my current ideas are listed roughly below:

• Try to make everything as concurrent as possible (Make network based tests as concurrent as possible #4271)
• Profile all tests and see what clogs up and fix that.
• solve the TODO in test_official.exceptions
• refactor test_sticker.py since sticker sets can now hold static, animated, and video altogether. #4514
• dirty-equals sounds like it could be quite useful for us!
• Think about renaming the Test*Base classes to just *Base since pytest collects the classes starting with Test*. Rename Testing Base Classes #4453
• Change CI's pytest --dist to worksteal Update pytest-xdist Usage #4491 .
• Extend that naming scheme to telegram.ext tests
• fix the class name

  python-telegram-bot/tests/test_menubutton.py

  Line 94 in 51ef571

  class TestMenuButtonselfBase:

  Rename Testing Base Classes #4453

Follow https://github.com/zupo/awesome-pytest-speedup, not all items but some are worth looking at:

• Introduce pytest-socket and completely disable network access for *WithoutRequest tests (PoC: pytest-socket like testing #4317, Make Tests for telegram.ext Independent of Networking #4454)
• Introduce pyfakefs to test suite (no major benefit found - Make network based tests as concurrent as possible #4271 (comment))
• Check if using uvloop in tests provides any measurable speed up.
• Isolate tests from other tests
• Check if introducing pytest-randomly (need to check if pytest-xdist effectively does the job of randomly)

-> Check if using pytest-asyncio-cooperative is worth it
- Nope it is not.