Add utility flow wait until done

[sklinglernv]

Description

Adds a wait until done utility flow into core.co that waits until a flow or action is finished or stopped. This intended to be used whenever the user is interested in whether a flow or action has finished but might miss the Finished() events, e.g. as part of when statements.

Checklist

• I've read the CONTRIBUTING guidelines.
• I've updated the documentation if applicable.
• I've added tests if applicable.
• @mentions of the person or team responsible for reviewing proposed changes.

[sklinglernv]

I like the naming changes and the split.

But I think the special treatment of flows is not necessary and we should make the CSL example simpler for users to understand (we can keep the test but move it into our unit test folder)