Rewriting phone constants for mainline

* Exposing Emergency extra constants through TelephonyManager
* Always reading or writing PhoneConstants.SubscriptionKey
with SubscriptionManager.EXTRA_SUBSCRIPTION_KEY

Bug: 147465477
Test: TeleServiceTests
Merged-In: I9cf495f19f3a752459ed67aa21bf6e0510a66547
Change-Id: Idfdecfdec80d21fcdd159c1e3e33b2bc2322d7ad
3 files changed