sout: implement a SetPCR callback in stream output
For a more global context on these changes, please have a look at #27050.
This is the first step for the SetPCR
implementation in stream output. These callbacks will allow stream outputs to have precise information about the stream time advancement.
This merge request only provides the basis for now, a correct implementation for all stream filters will come in a separate merge request.
Edited by Alaric Senat