DO NOT MERGE - Added Emergency affordance feature

Added a service that listens whether emergency affordances
are necessary.

If the they are needed, it adds an option to the
global actions dialog that directly launches the
emergency call and also adds a long-press listener
to the keyguard emergency button.

Test: adb shell settings put global force_emergency_affordance 1 && adb shell settings put global emergency_affordance_number 111112
Bug: 30404490
Change-Id: Ib96a15da2ef4b568a8d77140ebca6aa6f20f5ddb