CLI tests using xcp_d.cli.run.main() do not contribute to coverage

[tsalo]

Summary

In #1152, I've started using xcp_d.cli.run.main() to run the XCP-D workflow in tests, but for some reason, even though the tests run successfully, CodeCov doesn't detect that they've run the actual workflows, interfaces, etc. I'm not sure why that is, but it would be great to fix it, since switching over would drop the package's coverage from 83.21% to 66.66%.

In the meantime, I've kept the old way of running the tests and have only switched to the cleaner way for one of the integration tests. I'd very much like to move completely to the cleaner way in the future.

[tsalo]

Also using the MultiProc nipype config means non-main tests don't contribute to coverage either.