Draft: screencastService: Add Gstreamer pipelines for AV1 encoding

Open Robert Mader requested to merge rmader/gnome-shell:recorder-av1 into main

AV1/libaom is used for videochat these days and as of Gstreamer 1.22 has support for a realtime profile. Thus let's use it if a recent version of av1enc (with support for the usage-profile property) is available.

Prefer the .webm container format instead of .mp4 or .mkv as it's apparently best supported in practice and doesn't have license issues.

Draft until some further testing was done. Also additional property tweaking may be needed, especially for slow devices.

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