CI upload coverage to codecov for jobs other than database
Currently, it seems that the only job which uploads coverage reports to codecov is https://github.com/pandas-dev/pandas/blob/master/.github/workflows/database.yml

Ideally, the jobs in https://github.com/pandas-dev/pandas/blob/master/ci/azure/posix.yml would also upload coverage reports to codecov

Marking as "good first issue" as it doesn't require knowledge of the pandas codebase, though probably requires some experience/knowledge of CI systems