Add outPtr method from upstream.
Add a debug category for MediaSource.
New base class for trackprivateclient.

Add new files for tracks support.

Add new files for tracks support.
Add new files for tracks support.
Fix debug logs to not use toString.
Backport some more changes from upstream.
The GStreamer source element was rewritten by Sebastian Droge in bugzilla #139441.
Claim we support all media source types for now.