[lib] Remove unused utilities and validators

Summary:
Part of ENG-6366 : Rename MinimallyEncodedRawThreadInfo to RawThreadInfo

Noticed a coouple of functions were completely unused and could be removed. Flipped on "Unused function" inspection in my IDE and found a ton of similar functions throughout the codebase, but just addressing the ones in files I'm working with right now.

Depends on D10724

Test Plan: None of these were used anywhere, flow

Reviewers: ashoat, ginsu, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D10725