Implement PUSH_BLANK_BUFFERS_ON_STOP in Codec2

PUSH_BLANK_BUFFERS_ON_STOP is a MediaCodec feature that instructs a
codec to display a blank frame at end of playback on codecs configured
with an output surface.

The feature has existed for a while and been implemented for OMX-based
codecs, but it was missing from the newer Codec2-based codecs.

Test: atest DecoderPushBlankBuffersOnStopTest#testPushBlankBuffersOnStopAvc
Bug: 210587592
Change-Id: I3ec3117e991224134cb6cb6b6a601e063e96be26