cleanup a few refs

[aaazzam]

In refactoring the Prefect client, two "heavy" refs slipped by:

• prefect.states.Scheduled which imports all its friends and inflates memory
• prefect.client.schemas.sorting enums. Enums suck here, because you have to import them in order to set defaults, but since our imports are a little wonky to begin with, you end up importing every model just to set a default. So the one place this is used (which is inconsistent with other methods anyway) in logs, the sort is now optional and the default logic is moved inside the body of the function.

[codspeed-hq]

CodSpeed Performance Report

Merging #16586 will not alter performance

_{Comparing rm-heavy-refs (2469e5d) with main (488e7b4)}

Summary

✅ 3 untouched benchmarks