Test suite maintainence and new ideas

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 (#4271)
• Profile all tests and see what clogs up and fix that.
• solve the TODO in test_official.exceptions
• #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*. #4453
• Change CI's pytest --dist to worksteal #4491 .
• Extend that naming scheme to telegram.ext tests
• fix the class name https://github.com/python-telegram-bot/python-telegram-bot/blob/51ef571a0761bbfea136c455bbfa67d47b20585c/tests/test_menubutton.py#L94 #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 (#4317, #4454)
• Introduce pyfakefs to test suite (no major benefit found - https://github.com/python-telegram-bot/python-telegram-bot/pull/4271#issuecomment-2127968133)
• 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.