[web] introduce useAddMembersListUserInfos

Summary:
PLEASE NOTE THAT THIS DIFF AND SUBSEQUENT DIFFS IN THIS STACK WILL NOT BE LANDED UNTIL MORE OF THE REDESIGN IS READY SINCE THIS WILL CAUSE REGRESSIONS IN PROD

There is a a lot business logic for searching + selecting the users for the add members logic. To keep things better organized + have the add members modal follow a similar pattern to the add friends modal, I created a new hook called useAddMembersListUserInfos to house all the business logic for searching + selecting the users

Depends on D10941

Test Plan: flow + confirmed I was getting the same results for the add members modal

Reviewers: atul, inka

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10942