[lib] Refactor thread reducer

Summary:
issue: ENG-5814
We want to remove the thread related to the ks the user has logged in to / logged out of / had the cookie invalidated by.

Test Plan:
Tested that when keyserverAuthActionTypes.success is dispatched the threads are deleted and replaced with the new ones
Checked that when a user logs out the threads are deleted.

Reviewers: michal, kamil, ginsu, ashoat

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10620