gstsink: Add support for DMABuf import and graphics offload

By implementing support for GdkDmabufTextureBuilder and GstVideoInfoDmaDrm. This allows zero-copy video playback on Wayland when paired with hardware video decoding.

Can be tested with gtk4-demo --run=video_player

On Weston, plane-only composition even works with content / an overlay on top.

Tested devices:

• recent Intel devices (VA-API), 4K@60ps
• AMD Radeon RX 6700 XT (VA-API), 4K@60pfs
• Raspberry Pi 4b (V4L2 stateful / m2m), 1080p@60fps *
• Pinebook Pro / RK3399 (V4L2 stateless), 4K@60fps

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Additionally requires:

• Gstreamer 1.23 / main
• https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5890 (V4L2-SL/stateless only)

*: no pubilc patches for stateful V4L2 Gstreamer yet

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See also:

• guidog/livi!35 (merged)
• https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/issues/441
• mutter!3177 (merged) (Mutter only)