Should popup the confirmation toast after clicking the reset button.

Goal: Users may not notice what the change after resetting all settings configs in the Text and reading options. So we will use the toast to give nice feedback for them.

Fix: 220126995
Test: make RunSettingsRoboTests  ROBOTEST_FILTER=TextReadingPreferenceFragmentTest
Change-Id: Ife42b0c9d8a0241d7b8c3e5dbe7f9f1e2a6d759a