Implement Flash Notifications UI for Settings app.

Bug: 237628564
Test: make RunSettingsRoboTests ROBOTEST_FILTER=CameraFlashNotificationPreferenceControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=ColorSelectorLayoutTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=FlashNotificationsPreferenceControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=FlashNotificationsPreferenceFragmentTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=FlashNotificationsPreviewPreferenceControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=FlashNotificationsPreviewPreferenceTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=FlashNotificationsUtilTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=ScreenFlashNotificationColorDialogFragmentTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=ScreenFlashNotificationColorTest
Change-Id: I0987590ddfcfd0873ec419db263f6a7eade81844
Signed-off-by: yw.bae <yw.bae@samsung.corp-partner.google.com>
Signed-off-by: Angela Wang <angelala@google.com>