bug: covr::codecov() should throw an error if unable to upload coverage results to codecov.io

[ALanguillaume]

Description

covr::codecov() should throw an error if unable to upload coverage results to codecov.io

Actual Behaviour

If covr::codecov() fails to upload coverage results to codecov.io it does not throw an error, the corresponding github action is thus marked as successful in github.

The devs are not notify that there was a failure in the workflow.

See this workflow

Expected Behaviour

covr::codecov() throws an error if unable to upload coverage results to codecov.io.
-> gh action workflow fails
-> devs are notified

Additional context

Related to r-lib/actions#822