baseparse: Restrict query/convert responses when demuxing
baseparse: Restrict query/convert responses when demuxing

If the parser is not parsing a raw elementary stream, restrict
the position, duration and conversion query replies to
things we can sensibly answer about - especially don't do
random conversions to/from bytes.

StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer