[web] update add users list item ui

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

The add users modal is getting a brand new ui + ux. This diff updates the add users list item ui to match the new checkbox ui/ux.

For context here is what the new add users modal looks like:

Linear task: https://linear.app/comm/issue/ENG-5957/update-the-ui-of-add-friends-modal

Depends on D10719

Test Plan:
Please see the screenshot below

Reviewers: atul, inka

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10722