Add isConfirmationPromptSupported() method.

This will be used by the android.security.ConfirmationDialog.isSupported() and
is intended so that apps can know ahead of time whether the device implements
the ConfirmationUI HAL.

Bug: 63928580
Test: Manually tested.
Change-Id: I6347824b4e2330a93b7a7ffd7cf5b206009a564e
diff --git a/keystore/key_store_service.cpp b/keystore/key_store_service.cpp
index d59966f..d808c57 100644
--- a/keystore/key_store_service.cpp
+++ b/keystore/key_store_service.cpp
@@ -1787,6 +1787,10 @@
     return mConfirmationManager->cancelConfirmationPrompt(listener, aidl_return);
 }
 
+Status KeyStoreService::isConfirmationPromptSupported(bool* aidl_return) {
+    return mConfirmationManager->isConfirmationPromptSupported(aidl_return);
+}
+
 /**
  * Prune the oldest pruneable operation.
  */