Log Message:
gstreamer1: update to 1.20.2

Highlighted bugfixes:

* avviddec: Remove vc1/wmv3 override and fix crashes on WMV files with
  FFMPEG 5.0+
* macOS: fix plugin discovery for GStreamer installed via brew and fix
  loading of Rust plugins
* rtpbasepayload: various header extension handling fixes
* rtpopusdepay: fix regression in stereo input handling if sprop-stereo
  is not advertised
* rtspclientsink: fix possible shutdown deadlock
* mpegts: gracefully handle "empty" program maps and fix AC-4 detection
* mxfdemux: Handle empty VANC packets and fix EOS handling
* playbin3: various playbin3, uridecodebin3, and playsink fixes
* ptpclock: fix initial sync-up with certain devices
* gltransformation: let graphene alloc its structures memory aligned
* webrtcbin fixes and webrtc sendrecv example improvements
* video4linux2: various fixes including some fixes for Raspberry Pi users
* videorate segment handling fixes and other fixes
* nvh264dec, nvh265dec: Fix broken key-unit trick modes and reverse playback
* wpe: Reintroduce persistent WebContext
* cerbero: Make it easier to consume 1.20.1 macOS GStreamer .pkgs
* build fixes and gobject annotation fixes
* bug fixes, security fixes, memory leak fixes, and other stability and
  reliability improvements