Fixes #14560.

Summary

• use pytest's defensive safe_getattr helper when automatic parametrization ID generation probes __name__
• fall back to the argument/index ID when a parameter value raises during __name__ lookup
• add a regression test and changelog fragment

Verification

• red before fix: python -m pytest testing\python\metafunc.py::TestMetafunc::test_idval_ignores_broken_name_attribute -q failed with KeyError: '__name__'
• python -m pytest testing\python\metafunc.py::TestMetafunc::test_idval_ignores_broken_name_attribute -q
• python -m pytest testing\python\metafunc.py -q
• python -m ruff check src\_pytest\python.py testing\python\metafunc.py
• python -m ruff format --check src\_pytest\python.py testing\python\metafunc.py
• git diff --check