Add a global override for VoLTE calls (which leaves user setting in place)

Bug: 18446228
Change-Id: I7d07f066e5933c2aeecf9222bb54da69975099bc

core/java/android/provider/Settings.java

@@ -6607,6 +6607,14 @@ public final class Settings {
          */
         public static final String ENHANCED_4G_MODE_ENABLED = "volte_vt_enabled";
 
+        /**
+         * Global override to disable VoLTE (independent of user setting)
+         * <p>
+         * Type: int (1 for disable VoLTE, 0 to use user configuration)
+         * @hide
+         */
+        public static final String VOLTE_FEATURE_DISABLED = "volte_feature_disabled";
+
         /**
          * Whether user can enable/disable LTE as a preferred network. A carrier might control
          * this via gservices, OMA-DM, carrier app, etc.