[lib] Properly handle server call timeout when accepting an invite link

Summary:
We should distinguish timeout errors from other types.

https://linear.app/comm/issue/ENG-8958/invite-invalid-when-trying-to-join-the-comm-community

Depends on D13000

Test Plan: Modify thread join timeout to 10ms, accept a link and verify that the timeout message is being shown. Also verified that accepting the link still works with the original timeout.

Reviewers: kamil, inka

Reviewed By: inka

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13001