[lib] Fetch ENS names in useThreadSearchIndex

Summary: Depends on D6479

Test Plan: I verified that the web app was returning results when I searched for ashoat.eth (not logged in as ashoat.eth), when it previously didn't. It's returning all of the chats that the viewer is in with ashoat.eth

Reviewers: atul

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D6480