[lib] Don't created thin thread if call to identity server failed when adding friends

Summary:
https://linear.app/comm/issue/ENG-9509/accepting-a-friend-request-on-web-creates-thin-thread

Related discussion: https://phab.comm.dev/D13940#389316
Now we're throwing an error just in useUpdateRelationships(), there are no changes in getUserIdentities()
and useUsersSupportThickThreads() returns Map instead of Set

Depends on D14022

Test Plan:
Throw some error in fetchUserIdentitiesPromise() so that finding user indentity always fails
Mobile user goes to profile -> Friend list and adds the web user as a friend
Before a thin thread was created. Now mobile user sees an alert, because there is no auxUserInfo, no thick thread and call to identity server fails.

Reviewers: kamil, tomek, ashoat

Reviewed By: ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D14023