assistant: Restructure ambient context in preparation for adding more (#11822)

This PR restructures the ambient context in the `assistant` crate to
make it more amenable to adding more kinds of ambient context.

Release Notes:

- N/A
ba4d4c8e1cMarshall Bowers committed on 5/14/2024, 9:03:39 PM· committed by GitHubparentbf44787
4 files changedLine totals unavailable