Add a way for compositors to request a new buffer for a surface

On GPU resets, the compositor will loose its GPU copy of the wl_shm client buffers. These kind of clients have no way to know that a GPU reset has happened.

The compositor can re-create their GL/Vulkan state, but they no longer have anything to display if they released the client shm buffers. Keeping the last submitted shm buffer unreleased is not a good option either because it regresses performance.

It would be nice to have an extension to:

• Allow compositors to request a new buffer for a surface.
• Allow clients to indicate that they support this behavior.