This change also tightens `FakeVideoRenderer` to only 'handle' buffers
that are close to the current playback position.
This condition controls whether the renderer fires `onVideoSizeChanged`
and `onRenderedFirstFrame`, both of which should only be fired once the
frame has been 'released' to the screen, which in a real renderer
happens much closer to 'current position' than the existing 250ms of
`FakeRenderer.SOURCE_READAHEAD_US`.
A later change uses `VideoFrameMetadataListener` to test ExoPlayer
behaviour in scrubbing mode.
PiperOrigin-RevId: 740763283
96bb777484