devl/py-pip: Update to 7.0.3

• Update to 7.0.3
• Update pkg-plist
• USE_GITHUB to get test suite (PyPI sdist doesnt include them)
• Add TEST_DEPENDS and canonicalise regression-test: target
• Patch setup.cfg so that tests run properly
• Temporarily patch out versioned console_script's (pipX, pipX.Y) until USE_PYTHON=concurrent supports more granularity (coming soon).

Note: A couple of tests fail because of these missing console_scripts.

• Add USE_PYTHON=concurrent support accordingly.

While I'm here:

• Makefile: Sort sections
• Makefile: Whitespace align

Changes:

https://pip.pypa.io/en/stable/news.html

PR: 200688
Approved by: nivit (maintainer)