Clarify capabilities granted by CALL_PHONE permission.

Make it clear in the permission description string that CALL_PHONE can
put used to change call forwarding settings.

Also clarify API docs to indicate that MMI codes are dialable.

Bug: 268341970
Test: Docs only change.
Change-Id: Ia33c267ae262d5ed4c7eaad7f2f3c942b44252ad

core/res/AndroidManifest.xml

@@ -1466,6 +1466,9 @@
 
     <!-- Allows an application to initiate a phone call without going through
         the Dialer user interface for the user to confirm the call.
+        <p>
+        <em>Note: An app holding this permission can also call carrier MMI codes to change settings
+        such as call forwarding or call waiting preferences.
         <p>Protection level: dangerous
     -->
     <permission android:name="android.permission.CALL_PHONE"

core/res/res/values/strings.xml

@@ -1462,7 +1462,8 @@
       without your intervention. This may result in unexpected charges or calls.
       Note that this doesn\'t allow the app to call emergency numbers.
       Malicious apps may cost you money by making calls without your
-      confirmation.</string>
+      confirmation, or dial carrier codes which cause incoming calls to be
+      automatically forwarded to another number.</string>
 
     <!-- Title of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
     <string name="permlab_accessImsCallService">access IMS call service</string>