Consolodate ImsManager polling into class

Consolodates the logic in the platform used
to poll for ImsManager changes and notifications
and moves it into a helper class. This reduces
the duplication of backoff and retry logic.

Bug: 72643077
Test: Telephony Unit Tests
Change-Id: I3c38f878b0b5c64e8822f42f097f6c3201dec915