Support editable_wheel with setuptools>=64

[casperdcl]

On the subject of pip install -e, --editable woes, I've seen #697, #370, #436, #616, #585, #579, and also tried #582, #546 (comment), #546 (comment).

I think I have a different issue (setup.py develop works but pip install -e does not). Probably related to #737 (comment).

Added print(sys.argv) into setup.py for some debugging. This gives:

1. ✅ works fine (normal install):

# pip install .
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'egg_info']
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'dist_info', '--output-dir', '/tmp/pip-modern-metadata-5jbkp8ic', '--keep-egg-info']
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'bdist_wheel', '--dist-dir', '/tmp/pip-wheel-tkgf3n8x/.tmp-nc33bf8_']

2. ✅ works fine (editable install, creates ./_skbuild, ./cmake, ./mylib/ext.so):

# python setup.py develop
['setup.py', 'develop']

3. ❌ doesn't work (editable install, DOES NOT create ./_skbuild, ./cmake, ./mylib/ext.so)

# pip install -e .
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'egg_info']
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'dist_info', '--output-dir', '/tmp/pip-modern-metadata-10kn81k6', '--keep-egg-info']
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'editable_wheel', '--dist-dir', '/tmp/pip-wheel-ufrvs40p/.tmp-d90gwcg9']

4. ✅ works fine on setuptools<64 (editable install, creates ./_skbuild, ./cmake, ./mylib/ext.so)

# pip install -e .
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'egg_info']
['.../pip/_vendor/pyproject_hooks/_in_process/_in_process.py', 'dist_info', '--egg-base', '/tmp/pip-modern-metadata-lvcwha5j']
['setup.py', 'develop', '--no-deps']

[henryiii]

setup.py develop triggers the old, deprecated codepath in setuptools which we support. The new one requires an output mapping, I believe, which we should be able to get in scikit-build-core, but would be much harder to produce here.

scikit-build-core supports modern pip editable mode in native mode, if that's helpful. I'm hoping to add support for editable installs in the setuptools mode, in which case scikit-build would get that for free when we switch backends to scikit-build-core.