Add pre-commit config for flake8 (#8068)

This makes it easier to lint your own work with `pre-commit`, but doesn't change the CI config by adding this to the pre-commit.ci skip list.

There's no way to automatically reflect the additional dependencies from the requirements file, so the flake8 plugin list needs to be a verbatim copy.

resolves #7991

requirements-tests.txt

@@ -2,6 +2,7 @@ mypy==0.960
 pytype==2022.6.6; platform_system != "Windows"
 # must match .pre-commit-config.yaml
 black==22.3.0
+# must match .pre-commit-config.yaml
 flake8==4.0.1
 flake8-bugbear==21.11.29
 flake8-pyi==22.5.1