demux: ts: Better missing PCR fixes

Moves the PCR fix from a global to program focused one.

Replaces the program PCR with a selected one instead of
sending PCR updates from all streams (applies to --no-trust-pcr)

Queues blocks until PCR appears. (will help fixing offsets)

Changes PCR probing time from 100ms (spec max) to 0.5s
(seen some streams with 0.4s inter-PCR)