Improved autofill support on DatePicker and TimePicker:

- Save autofilled value so UI is properly highlighted.
- Notify TimePicker listener just once.

Test: cts-tradefed run commandAndExit cts-dev -m CtsAutoFillServiceTestCases
Test: cts-tradefed run commandAndExit cts-dev -m CtsWidgetTestCases -t android.widget.cts.DatePickerTest
Test: cts-tradefed run commandAndExit cts-dev -m CtsWidgetTestCases -t android.widget.cts.TimePickerTest

Fixes: 37098837

Change-Id: I38d64c107f6059b94c92676ea37681006474f519