🧪 Fixes and simplifications to tests

[mattmess1221]

Most important change is the added conftest.reset_imports fixture, which restores the state of sys.modules after each test, similar to conftest.resset_syspath.

Other changes rewrites duplicated tests to use pytest.mark.parametrize and replaces tests.utils.changing_dir to use monkeypatch.chdir

[github-actions]

This pull request has a merge conflict that needs to be resolved.