This restores the Python wheel CI runs from the old upb repo with only minor
changes. I had to update a path in one of the `py_wheel` rules and also make a
slight tweak to ensure that the `descriptor.upb_minitable.{h,c}` files make it
into the source wheels. The change in text_format_test.py is not strictly
necessary but is a small simplification I made while I was trying to debug an
issue with CRLF newlines.
I had to update test_util.py to use `importlib` to access the golden files from
the installed `protobuftests` package. I suspect the previous incarnation of
thse test runs was somehow reading the goldens from the repo checkout, but I
think the intention is to read them from `protobuftests` instead. This was a
bit tricky to get working because Python versions before 3.9 do not support
`importlib.resources.files()`. I set up the code to fall back on
`importlib.resources.open_binary()` in that case, but that function does not
support subdirectories, so this required putting an `__init__.py` file inside
the `testdata` directory to make sure it is treated as a Python package.
PiperOrigin-RevId: 567366695
