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: FrameworksCoreTests, FrameworksServicesTest, CarrierTests
Merged-In: I84d6687ca6cab86c8c68dc2dd2679cfee0919c1e
Change-Id: Ic02e02a4b1ac989a974938dc87118a6f7c926e9e