Add looponfailrootsignore option

[Harshal96]

Thanks for submitting a PR, your contribution is really appreciated!

Checklist:

• Make sure to include reasonable tests for your change if necessary
• Add a towncrier news file in the changelog folder

Summary:

• Add --looponfailrootsignore and looponfailrootsignore support for loop-on-fail file watching.
• Ignore matching generated files and directories in StatRecorder so artifacts like cassettes or databases do not trigger endless reruns.
• Document the looponfailroots and looponfailrootsignore settings.

Test plan:

• uv run pytest
• uv run --with pre-commit pre-commit run --all-files --show-diff-on-failure
• uv run --with tox tox -e py310-pytestlatest

Closes #633