Handle uninstall result - caller does not want the result back.

When the caller does not request the uninstall result, we show a toast in cast of a successful uninstall and a notification in case of a failed uninstall.

Bug: 182205982
Test: builds successfully
Test: No CTS Tests. Flag to use new app is turned off by default

Change-Id: I10342c9f9ab83c418afd74479b9f04e7837e6545