[lib] Introduce relyingOnAuthoritativeKeyserver constant

Summary:
This diff starts the process of splitting usingCommServicesAccessToken into three:

1. usingCommServicesAccessToken: flipped to true for identity service launch
2. supportingMultipleKeyservers: whether the app works with multiple keyservers, which relies on Tunnelbroker to sync data (eg. keyservers and users) and the backup service to restore that data
3. relyingOnAuthoritativeKeyserver: whether the app needs to have a cookie with the authoritative keyserver in order to be considered logged in

These will all be separate launch processes, so I figured it made sense to have three separate constants.

In this diff I introduce relyingOnAuthoritativeKeyserver. In the following diff I'll update reducers to use relyingOnAuthoritativeKeyserver to decide whether to log the user out during a SET_NEW_SESSION with cookieInvalidated.

Depends on D11227

Test Plan: I used this test plan for the whole stack: https://gist.github.com/Ashoat/75ab690d5c53cdd68a51b02e03e27c58

Reviewers: inka, tomek

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D11228