pyemscripten/pyodide wheel builds

[greateggsgreg]

Enable building pyemscripten/pyodide wheels. Now that https://peps.python.org/pep-0783/ is accepted, Pyodide/PyEmscripten wheels (specifically the Pyemscripten ABI (2026_0) ) are allowed to be published on PyPI.

This should also remove the need for pyodide-recipies to maintain a pynacl wheel build script out of tree.

Remaning tasks:

• cibuildwheel with pyemscripten support should be merged: Pyodide updates: pyemscripten platform tag (PEP 783), 314.0a1, pyodide-eol flag, and maintenance updates pypa/cibuildwheel#2812
• Revise wheel-builder.yml logic to not use a development build of cibuildwheel once a release containing cibuildwheel#2812 is published. (Currently installing from pypa/cibuildwheel@main now that #2812 is merged.)
• Ensure full test suite is run

Any other thoughts based on the current PR? #947