Initialize notifications olm account in CommCoreModule and expose notifications public keys to JS

Summary: This differential uses NotificationsCryptoModule API to idempotently create notifications olm account and to expose notifications public keys in JS via JSI.

Test Plan: Modify one place in JS native code where we call getUserPublicKeys to log notifications public keys to the console. Example of such place is log-in panel. Launch the app and examine console.

Reviewers: tomek, kamil, atul, bartek

Reviewed By: kamil, atul, bartek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D6781