Listeners of active emergency numbers

1) Introduce a new signature-level system permission allowing system apps to listen the
 active emergency number, placed by calls or texts.

2) Add PhoneStateListener API surface to provide a mechanism to listen the
outgoing call emergency number or outgoing sms emergency number.

Bug: 135204580
Test: atest
Change-Id: I6e6bce6d4b97d492ca20302002911f9daa20767e
Merged-In: I6e6bce6d4b97d492ca20302002911f9daa20767e
(cherry picked from commit 7a1eb6d5)