split tests into two steps, report ok and done separately (#3646)

This removes some long running tests (mac and windows) from the required
PR checks.

Now the CI workflow is split into two parts, `Ok` (required) for the
required checks and `Done` (non-blocking) for all checks.

The PR comment will show

🟢 CI likely successful 🟢
A few longer running steps are still running, but they should not be
considered as blocking.

See workflow summary for details

after the required checks are done.

Once all checks are done, it will be updated to 🟢 CI successful 🟢 or to
⚠️ CI failed ⚠️ depending on the full result

Author: sokra