[web] Don't allow creating subchannels with users the user should not be able to add

Summary:
issue: ENG-8710
The user should not be able to add some users to some chats. On native we handle this in the UI by showing a popup if the user wants to add someone they cannot.
On web we decided that for now we will just not display those users. Handlig tih siwth a popup is tracked in ENG-8798

Property alert is set only when the user cannot be added to the thread. There are four cases. They can be found in lib/shared/search-utils.js in usePotentialMemberItems.

Test Plan: Tested that in all four cses the users don't show up in search results on web anymore.

Reviewers: tomek, kamil, ashoat

Reviewed By: tomek, ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D12715