Don't limit DMA buffer screen casting only to Intel

Quoting the two one commit:

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backend/native: Only disable dmabuf screen cast when not hw accelerated

Don't attempt to predict whether we support DMA buffer screen casting
depending on EGL context type or driver name, but only whether we are
hardware accelerated. For all other cases, simply try and fall back to
shared memory if need be.

The reason we can do this now is that we only try to allocate DMA
buffers if the PipeWire client asked for it, and rely on that client to
know it can handle them.

However, in case we're not hardware accelerated, we never want to
attempt to use DMA buffer screen sharing, as we want to avoid
compositing into a DMA buffer on such hardware as doing so can be very
slow.

Related things that this relies on: https://gitlab.freedesktop.org/pipewire/pipewire/-/merge_requests/1067 and gnome-remote-desktop!63 (merged).