[lib] Create a selector that checks if a user is logged in to a keyserver

Summary:
Check if user is logged in and if the cookie exists and isn't anonymous.

Depends on D10814

Test Plan: Call a selector for keyserver with ashoatKeyserverID and check if it returns true. Add a new keyserver to the store and check if the selector returns false for it.

Reviewers: varun, inka, kamil

Reviewed By: inka

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D10830