Upgrade py-pytest-cov from 2.9.0 to 4.1.0

[ngie]

Summary

This is required so py-pytest-cov is functional with newer versions of
py-pytest-xdist [1].

While here, appease portlint by shifting where variables (CONFLICTS,
etc) are defined.

1. https://github.com/pytest-dev/pytest-cov/issues/422

PR: 269360
Co-Authored By: Yuri Victorovich <[e-mail]>

Test Plan

make test passes with this change.

[ngie]

patch-setup.py isn't strictly required I suppose. I can remove it from the diff, if need be.

[ngie]

Update package to 4.1.0

Remove now obsolete patches.

Tested with: make test

[yuri]

Can/should this be committed?

[ngie]

In D39035#949271, @yuri wrote:

Can/should this be committed?

Yes. I'll take this item since I have it checked out in a ports tree and I need to rebase anyhow.

I have a src bit (not a ports bit), which is why I haven't been committing tons of ports updates :/.