[keyserver] Replace ashoatKeyserverID with thisKeyserverID()

Summary:
issue: ENG-6633
Replacing ashoatKeyserverID with calls to fetchIdentityInfo - because this is async I had to make a couple of functions that need it be async as well.

Test Plan:
Tested that state sync still works by logging infosHash in checkState and compoaring with values returned by the previous code, on a client in with the same state.
Tested that the id is fetched correctly in getInitialReduxStateResponder and validateOutput (by checking that ids are prefixed correctly)

Reviewers: michal, tomek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11050