useSearchUsers is used to include user search results from the server (outside of the user's local userStore during the 'composing a new chat' flow on both web and native.
The code looks a little like the code in AddUsersList on web and RelationshipList on native when viewing your friends. Because of this, this diff is really useful in getting rid of a 'one off' search logic
and instead using a shared search helper. This will make it easier to do the next part of this stack (updating search helpers to lookup addresses from a typed out ENS name).
Addresses ENG-5490
Depends on D9883