Adding support for external stimulus release event in the

SeekableSliderEventProducer.

The event when a seekable slider is released from external stimulus
control (e.g., a button or a physical key) is now produced by the
SeekableSliderEventProducer.

Test: atest SystemUITests:SeekableSliderEventProducerTest
Bug: 316953430
Flag: NONE
Change-Id: I3026085580f84e0ee4ddae48ce811071a97fdf61