tmf/ctf: Show trace read progress in the progress bar

tmf/ctf: Show trace read progress in the progress bar

This patch adds an interface : ITmfTraceKnownSize. This interface
has two methods:
- size()
- progress()

If a tracetype implements these methods, the progress will show a scrolling
bar instead of the night-rider/battlestar galactica style slider of an
unknown progress bar.

Change-Id: If1b61957f26c2dec26543f64cfb42e12b127391c
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/67779
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Reviewed-by: Hudson CI