Create a helper lib for emergency numbers.

This util class manages getting/setting default emergency numbers,
shared by settings, EmergencyInfo and other clients.

The logic is copied from Personal Safety app - http://shortn/_Z7qtV6RpJG

Bug: 172609395
Test: manual
Change-Id: I9062d84f49556d2b7e7866c43d64dac55d48f4f4
diff --git a/packages/SettingsLib/Android.bp b/packages/SettingsLib/Android.bp
index 3af4b25..64dc2af 100644
--- a/packages/SettingsLib/Android.bp
+++ b/packages/SettingsLib/Android.bp
@@ -51,6 +51,7 @@
         "SettingsLibRadioButtonPreference",
         "SettingsLibDisplayDensityUtils",
         "SettingsLibUtils",
+        "SettingsLibEmergencyNumber",
         "SettingsLibTopIntroPreference",
     ],
 }