* ci: test on emscripten target
This adds CI to build libpython3.11 for wasm32-emscripten and
running tests against it. We need to patch instant to work
around the emscripten_get_now:
https://github.com/sebcrozet/instant/pull/47
We also have to patch emscripten to work aroung the "undefined
symbol gxx_personality_v0" error:
https://github.com/emscripten-core/emscripten/issues/17128
I set up a nox file to download and install emscripten,
download and build cpython, set appropriate environment variables
then run cargo test. The workflow just installs python, rust,
node, and nox and runs the nox session.
I xfailed all the test failures. There are problems with datetime.
iter_dict_nosegv and test_filenotfounderror should probably be
fixable. The tests that involve threads or asyncio probably can't
be fixed.
* Some cleanup
* Remove instant patch
* Add explanations for xfails
