v0.25.2: DTS-HD codec ID + PGS BlockDuration

- MkvTrack::audio emits A_DTS/MA, A_DTS/HR, A_DTS per the DTS family
  instead of mislabelling everything as A_DTS. Plex transcoder and
  strict hardware decoders reject DTS-HD MA payload under a plain
  A_DTS track.
- PgsParser is now stateful: pairs display PCS with the following
  empty PCS to compute a duration. Frame::duration_ns + PesFrame::duration_ns
  carry it through; MkvMuxer::write_frame gains a final Option<u64>
  parameter that emits BlockGroup + BlockDuration when set. Fixes
  subtitle bitmaps lingering past their intended end-time.

src/mux/pipelined_stream.rs

@@ -108,6 +108,7 @@ impl PipelinedPesStream {
                         pts: pes.pts.map(super::codec::pts_to_ns).unwrap_or(0),
                         keyframe: false,
                         data: pes.data,
+                        duration_ns: None,
                     });
                 } else if let Some((_, parser)) =
                     self.parsers.iter_mut().find(|(pid, _)| *pid == pes.pid)