[lib] Introduce MinimallyEncodedResolvedThreadInfo and start refactoring
Summary:
We introduce MinimallyEncodedResolvedThreadInfo and start refactoring to accomodate the type everywhere that ResolvedThreadInfo is.
This diff handles a lot of the "simple stuff." The trickier stuff, specifically w/ useResolvedThread* hooks will be resolved in subsequent diffs.
Depends on D9895
Test Plan: Trusting flow here.
Reviewers: ashoat, ginsu, tomek, rohan
Reviewed By: ashoat
Differential Revision: https://phab.comm.dev/D9896