[CLI] Better handle empty upload notifications

[drazisil-codecov]

When a customer needs a passing check for a PR when they did not upload coverage, the recommended way is currently to call empty-upload --force with the CLI.

This works, except in cases where the "empty report" needs to do work, such as loading carry forward flag coverage. codecov/engineering-team#2365

I propose that a sequence of CLI commands such as this will work

• create-commit
• create-report
• empty-upload
• get-report-results until you get a reply
• send-notifications

We need a better way.