Refactor requirementslib for modern pip 22.1

[matteius]

I am not entirely sure what this entails yet, but this is to basically work towards being able to remove the utilities I copied in from older pip 21.x in order to fix the build with:
#321 and
#320

[oz123]

Wasn't this already fixed?

pipenv is already using pip==22.2.2

[oz123]

OK, This is related to this file which is still used:

https://github.com/sarugaku/requirementslib/blob/main/src/requirementslib/models/old_pip_utils.py