[3.13] gh-121735: Fix module-adjacent references in zip files (GH-123037) (#123986)

* gh-121735: Fix module-adjacent references in zip files (GH-123037)

* gh-116608: Apply style and compatibility changes from importlib_metadata.

* gh-121735: Ensure module-adjacent resources are loadable from a zipfile.

* gh-121735: Allow all modules to be processed by the ZipReader.

* Add blurb

* Remove update-zips script, unneeded.

* Remove unnecessary references to removed static fixtures.

* Remove zipdata fixtures, unused.
(cherry picked from commit ba687d9481c04fd160795ff8d8568f5c9f877128)

* gh-123994: Generate utf-16 file using little endian and BOM. (#123995)

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>