## Why are these changes needed?
This PR ensures that workflow can work properly with Ray client.
Regular workflow tests will (also) be running under client mode (as a pytest parameter). Some tests are moved and reorganized, because the Ray client tests requires starting the cluster, so some tests requires isolation or related changes.
Tests that literally take down the cluster are not tested with Ray client, since Ray client would fail in this scenario.
Limitations of Ray Workflow under Ray client are noted in the doc.
## Related issue number
Closes#21595
