[lib] Add threadInfoFromRawThreadInfo test to thread-utils.test

Summary:
Based on feedback here: https://phab.comm.dev/D10718?id=35839#inline-65319

Depends on D10812

Test Plan: Unit test passes.

Reviewers: ashoat, ginsu, tomek

Reviewed By: ashoat

Subscribers: rohan

Differential Revision: https://phab.comm.dev/D10818