PyPi: Support package upload

Implement PyPI package upload via the twine tool.

Details

Upload is performed using the Legacy API using a multipart/form-data POST request. Details on the fields sent can be found on the referred docs.

The upload process usually involves pushing 2 files, the raw source tar.gz data and the build distribution file .whl. Each file is pushed as an independent POST request.

Sample push command:

python3 -m twine upload --repository testpypi dist/*

Entry points

POST gitlab.com/api/v4/projects/:id/packages/pypi: The upload entry point for twine.

PUT gitlab.com/api/v4/projects/:id/packages/pypi/authorize: Internal authentication entry point for workhorse.

Authentication

Needs to support Authentication via basic HTTP auth to allow for either CI tokens or PAT.

See #34161 (closed) for full discussion.