Update test_peg_generator to not need distutils & reenable it #100238

distutils was removed from 3.12, as per PEP 632.
test_peg_generator, which uses it, was disabled. It should be updated to not need distutils.

See #92584

Linked PRs

• gh-100238: Vendor distutils for peg_generator #104744
• gh-100238: Use setuptools in peg-generator and reenable tests #104798
• [3.12] gh-100238: Use setuptools in peg-generator and reenable tests (GH-104798) #105135