Introduce utility method in CarrierConfigManager to get config subset

This CL introduces a hidden utility method for system components to
get the subset of carrier config.

Many system components has been update to use the new
CarrierConfigManager API to get subset of config. But the callers
side have repetitive private methods to do the same thing. The
utility method in CarrierConfigManager will remove the duplication.

Bug: b/263267340
Test: FrameworksTelephonyTests
Change-Id: Ifbd84c67525fd9ea2925e5b735788e6c3c22dd34

telephony/java/android/telephony/CarrierConfigManager.java

@@ -10694,4 +10694,38 @@ public class CarrierConfigManager {
         }
         trm.removeCarrierConfigChangedListener(listener);
     }
+
+    /**
+     * Get subset of specified carrier configuration if available or empty bundle, without throwing
+     * {@link RuntimeException} to caller.
+     *
+     * <p>This is a system internally used only utility to reduce the repetitive logic.
+     *
+     * <p>Requires Permission:
+     * {@link android.Manifest.permission#READ_PHONE_STATE READ_PHONE_STATE}, or the calling app
+     * has carrier privileges on the specified subscription (see
+     * {@link TelephonyManager#hasCarrierPrivileges()}).
+     *
+     * @param context Context used to get the CarrierConfigManager service.
+     * @param subId The subscription ID to get the config from.
+     * @param keys The config keys the client is interested in.
+     * @return Config bundle with key/value for the specified keys or empty bundle when failed
+     * @hide
+     */
+    @RequiresPermission(anyOf = {
+            Manifest.permission.READ_PHONE_STATE,
+            "carrier privileges",
+    })
+    @NonNull
+    public static PersistableBundle getCarrierConfigSubset(
+            @NonNull Context context, int subId, @NonNull String... keys) {
+        PersistableBundle configs = null;
+        CarrierConfigManager ccm = context.getSystemService(CarrierConfigManager.class);
+        try {
+            configs = ccm.getConfigForSubId(subId, keys);
+        } catch (RuntimeException exception) {
+            Rlog.w(TAG, "CarrierConfigLoader is not available.");
+        }
+        return configs != null ? configs : new PersistableBundle();
+    }
 }