wayland-dma-buf: Use alpha-less pixel formats where appropriate
From the main commit:
The XRGB/XBGR pixel formats do not set the cogl alpha bit. This
allows for example `MetaShapedTexture` to use the fast opaque
path for rendering and `MetaCullable` to detect whether a
`MetaSurfaceActor` is opaque.The typical use case here is client requesting a EGL config without alpha channel. Right now on an Intel iris driver it would usually end up with a XRGB2101010 format. Mutter would currently fail to detect this as opaque, making it either necessary to set an opaque region in the client or simply making us slower.
Closes #1733 (closed)
See also: !1756 (closed)
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9989