Code improvements for type hints

[cvzi]

• Fix some of the type: ignore in core.py and tokenizer.py
• Change pytest's import mode to importlib in pyproject.toml (necessary for next point)
• Move helper functions from tests into separate file utils/testutils.py
• Replace usage of private _EMOJI_UNICODE in tests
• Add an option to run tests in random order with pytest --shuffle
• Run tests in normal and random order in CI
• Upgrade CI to ubuntu-22.04
• Add pypy-3.10 to CI tests, we have listed pypy as supported, so we should test it