GStreamer1: Update to 1.28.4
Backport several security fixes from not-yet-released 1.28.5.
Add a create-vuxml target to multimedia/gstreamer1 to automagically
create a VuXML entry for new GStreamer releases. The backing script
can be used standalone for cases when more fine tuning is needed.
Changes:
https://gstreamer.freedesktop.org/releases/1.28/#1.28.4
Security: 4e82a0e6-6801-42c6-8fb6-91b6b275a9e1