tsparse: Implement timestamp/retimestamping of output buffers

tsparse: Implement timestamp/retimestamping of output buffers

When the set-timestamps property is set, use PCRs on the provided
(or autodetected) pcr-pid to apply (or replace) timestamps on the
output buffers, using piece-wise linear interpolation.

This allows tsparse to be used to stream an arbitrary mpeg-ts file,
or to smooth jittery reception timestamps from a network stream.

The reported latency is increased to match the smoothing latency if
necessary.