Handle requirements.txt more completely

[dannysauer]

The setuptools, wheel, and pip packages are in the requirements.txt now. That's not ideal. As a first thought, what I think should happen is the update_requirements make target should do two pip freeze operations, one with and one without --all specified. Then do a diff (perhaps using comm -3 requirements.txt setup_requirements.txt or perhaps just a grep) to pull those three out, and save the three versions in "setup_requirements.txt". Either way, the dependabot action will need updated to check that new file as well as requirements.txt, and the first pip install can just do pip install -U -r setup_requirements.txt.

More explicitly...

comm -3 \
  <(/opt/pulp/bin/pip freeze -r /opt/pulp/pulp-requirements.txt --local | sort) \
  <(/opt/pulp/bin/pip freeze -r /opt/pulp/pulp-requirements.txt --local --all | sort)

Possibly with the pulp-requirements.txt itself being mangled with a sed in the container instead of having the Makefile do a sed -i. This starts to get a tad complicated:

comm -3 \
  <(/opt/pulp/bin/pip freeze -r <( sed '/following requirements/,$d' /opt/pulp/pulp-requirements.txt ) --local | sort) \
  <(/opt/pulp/bin/pip freeze -r <( sed '/following requirements/,$d' /opt/pulp/pulp-requirements.txt) --local --all | sort)