Import GstVulkan{,Wayland,XCB}-1.0.gir from 2eee3f4ca4

Preparing for gstreamer-vulkan bindings in Rust, add the gir files necessary to build it.

Note that these files "don't really work yet™", pending how gstreamer!1615 (merged) unfolds (or not). But we'll at least have a nice diff on top showcasing the improvements proper annotations make.