Draft: Reapply "libcamera: Implement proper dmabuf negotiation support"
In order to allow clients to explicitely ask for DMABUFs.
This allows the following GST pipeline to have Wayland passthrough (and thus possibly offloading to display hardware): gst-launch-1.0 pipewiresrc ! gtk4paintablesink
This reapplies commit 950b62a8 This reverts commit bdc0720b.
Draft in order to do throughout testing and addressing the issue for the back-out.