[web] Introduce cryptoStore to replace primaryIdentityPublicKey in Redux

Summary:
Migrate from having primaryIdentityPublicKey in Redux to having the more flexible cryptoStore which will have both our primary identity keys AND notification identity keys.

Only the primaryIdentityPublicKey is being passed to the keyserver in the login/siwe_auth/register requests... so no behavior should change and this is effectively a "noop."

Depends on D6876

Test Plan:
Migration succeeded:

primaryIdentityPublicKey is set correctly in the database:

Reviewers: ashoat, tomek, marcin

Reviewed By: ashoat

Subscribers: kamil

Differential Revision: https://phab.comm.dev/D6877