Backport of #31397.

Summary

Closes #31392

This updates the Meson install rules to exclude __pycache__ directories from wheel contents
Issue was reported for wheels containing bytecode cache files such as:

numpy/distutils/__pycache__/conv_template.cpython-311.pyc

__pycache__ directories are generated locally during Python execution/compilation and should not be copied into built wheels.

Validation

Created a local __pycache__ directory under an installed pure Python subdirectory:

python -c "import py_compile; py_compile.compile('numpy/f2py/__init__.py')"
find numpy/f2py -name "__pycache__" -o -name "*.pyc"

Built the wheel:

python -m build -w

Confirmed no __pycache__ entries were included:

unzip -l dist/*.whl | grep __pycache__
unzip -l dist/*.whl | grep "numpy/f2py/__pycache__"

Both grep commands returned no output

AI was used to help draft the PR description and to sanity check local verification steps. The code change was made and tested locally by me.