mpegts_sr: add some resilience to transmission errors.
mpegts_pmt: rework stream probing to better suit transcoding.

Transcoding needs exactly one audio stream, which is
preferrably not a NARrative stream.
mpegts_sr/pmt: remove some debug logging.
cosmetics.
mpegts_pmt/sr: if pid not found in stream, don't persist.
debug: new debug code to go with new code.