Adding @hide to UpdateEngineStable

Adding hide annotation to ue stable APIs and updating interface version.
Freezing interface with version 2.

Test: m libupdate_engine_stable-V2-java
Bug: 317914533

Change-Id: Ice7d095b9a6903754ab76e1e097d941773119508
diff --git a/stable/android/os/IUpdateEngineStableCallback.aidl b/stable/android/os/IUpdateEngineStableCallback.aidl
index d8fc333..4f91c15 100644
--- a/stable/android/os/IUpdateEngineStableCallback.aidl
+++ b/stable/android/os/IUpdateEngineStableCallback.aidl
@@ -18,6 +18,7 @@
 
 /**
  * The stable Callback interface for IUpdateEngineStable.
+ * @hide
  */
 oneway interface IUpdateEngineStableCallback {
   /**
@@ -26,6 +27,7 @@
    * @param status_code see {@link android.os.UpdateEngine.UpdateStatusConstants}.
    * @param percentage percentage of progress of the current stage.
    * @see android.os.UpdateEngineCallback#onStatusUpdate(int, float)
+   * @hide
    */
   void onStatusUpdate(int status_code, float percentage);
 
@@ -34,6 +36,7 @@
    *
    * @param error_code see {@link android.os.UpdateEngine.ErrorCodeConstants}
    * @see android.os.UpdateEngineCallback#onPayloadApplicationComplete(int)
+   * @hide
    */
   void onPayloadApplicationComplete(int error_code);
 }