Flag an error if someone submits a pip package which will mask a native package

[tfoote]

Our policy is that we should not submit a pip package that will mask a system package.

This is something that is hard to review manually as it requires you to search for the same or similar names in the ubuntu and debian packages. It would be good to search the other platforms too.

it's easy to overlook the masking such as ros/rosdistro#44287

There was a one line comment in the orignal PR mentioning the masking, but the reviewers didn't see it.

We can at least catch the ones with exactly the same name, even better would be to detect the python module because some package names get edited, due to things like debian naming policy restrictions being stricter than PyPI

Example: https://packages.ubuntu.com/oracular/python3-pymongo vs https://pypi.org/project/pymongo/