[lib] Remove instances of LegacyThreadInfo from DrawerUtils

Summary:
Part of https://linear.app/comm/issue/ENG-6366/rename-minimallyencodedrawthreadinfo-to-rawthreadinfo

Prerequisite to deprecating LegacyResolvedThreadInfo which we should be able to remove completely since it's entirely a client "UI type."

Depends on D10646

Test Plan: flow

Reviewers: ashoat, ginsu, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D10654