Lint: run more flake8-pytest-style

[hugovk]

Expand from PT006 to all of PT:

https://docs.astral.sh/ruff/rules/#flake8-pytest-style-pt

Fix warnings for PT001, PT014 and PT018.

Exclude these which have warnings:

• PT007 pytest-parametrize-values-wrong-type
• PT011 pytest-raises-too-broad
• PT012 pytest-raises-with-multiple-statements
• PT016 pytest-fail-without-message
• PT017 pytest-assert-in-except

I'm fine if someone wants to tackle those in another PR.

[hugovk]

Changed my mind about PT001, let's skip it.