WGL does not have the concept of a `Display` connection, presumably
because there's always only one compositor active.  All interop
and sharing is happening from the `Context` afterwards.

After all `glutin` doesn't have a pointer inside `RawDisplay::Wgl`,
and upstream `gstreamer` code creates a dummy display on Win32.

WINRT is not taken into account & tested yet.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1468>