Raise the Python floor to 3.11 in 2.0; drop the last dependency

[derek73]

Python 3.10 reaches end-of-life in October 2026, around when 2.0 ships. Raising requires-python to >=3.11:

• Deletes the typing_extensions conditional dependency (needed only for Self on 3.10) — nameparser becomes a zero-dependency library
• Deletes the sys.version_info gate in config/__init__.py
• Updates classifiers and the CI matrix

3.11 (not 3.12) as the floor: Self is the only feature we need, and one extra supported version costs nothing. No code changes beyond the import cleanup; semver-wise this belongs in 2.0 with the other breaking changes.