Implement native public notifications API

Summary:
This differential implements public methods defined in CommIOSNotifications header. All method implementations apart from "clearNotificationFromNotificationsCenter" are identical with Ashoats fork. Implementation of "clearNotificationFromNotificationsCenter" was altered to match what we
currently do in rescindg code in AppDelegate

Test Plan: build the app. Subsequent diffs will use this API and hence will provide comprehensive test plan.

Reviewers: tomek, atul, ashoat

Reviewed By: tomek, ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D6067