With the Vulkan renderer we don't support implicit modifiers.
However wl_drm only supports implicit modifiers.
Stop advertising wl_drm formats when implicit modifiers are
unsupported.
Query the formats at init time, then forget about the renderer.
This will allow wl_drm to be created with a list of formats instead
of a renderer, and will behave better after a GPU reset.
This will allow us to remove all of our EGL wl_drm support code
and remove some weird stuff we need just for wl_drm support. In
particular, wl_drm buffers coming from the EGL implementation
can't easily be wrapped into a wlr_buffer properly.
