clover/spirv: rework handling of spirv extensions

clover/spirv: rework handling of spirv extensions

What extensions we support depends on spirv_to_nir but it doesn't give us a
list. So hardcode one and add extensions we know we support and hit in the
wild.

v2: move into spirv lib

Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Pierre Moreau <dev@pmoreau.org>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5038>