Keystore: Surface service error message

Surface the service-specific error message. To avoid API changes, the
error message is surfaced in the toString / getMessage methods.

Test: atest android.security.keystore.KeyStoreExceptionTest
Bug: 217593122
Change-Id: Id4090564b46db9b3b10ea390390f6683f7314463

keystore/java/android/security/KeyStoreException.java

@@ -157,6 +157,16 @@ public class KeyStoreException extends Exception {
         mErrorCode = errorCode;
     }
 
+    /**
+     * @hide
+     */
+    public KeyStoreException(int errorCode, @Nullable String message,
+            @Nullable String keystoreErrorMessage) {
+        super(message + " (internal Keystore code: " + errorCode + " message: "
+                + keystoreErrorMessage + ")");
+        mErrorCode = errorCode;
+    }
+
     /**
      * Returns the internal error code. Only for use by the platform.
      *