Add the following methods:
* assertHasAttr() and assertNotHasAttr()
* assertIsSubclass() and assertNotIsSubclass()
* assertStartsWith() and assertNotStartsWith()
* assertEndsWith() and assertNotEndsWith()
Also improve error messages for assertIsInstance() and
assertNotIsInstance().
* 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.
gh-116609: Ignore UTF-16 BOM in importlib.resources._functional tests
To test the `errors` argument, we read a UTF-16 file as UTF-8
with "backslashreplace" error handling. However, the utf-16
codec adds an endian-specific byte-order mark, so on big-endian
machines the expectation doesn't match the test file (which was
saved on a little-endian machine).
Use endswith to ignore the BOM.