gh-121735: Fix module-adjacent references in zip files (#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.