The coverage collection/reporting job is failing on CI

[exarkun]

{'detail': ErrorDetail(string='Commit sha does not match Circle build. Please upload with the Codecov repository upload token to resolve issue.', code='not_found')}

It seems like this is probably related to the de-support of the Python "codecov" package (https://about.codecov.io/blog/message-regarding-the-pypi-package/). Even if it is not, that's what we're using so we should probably stop.

There is a CircleCI orb so we could try using that, I suppose. Our current coverage CI config takes care to merge reports from all of our jobs before submitting to codecov because letting codecov do the merge has been flaky in the past. If we can't replicate this using the orb then we should consider something else.