intel/fs: Add support for bindless texture ops

intel/fs: Add support for bindless texture ops

We add two new texture sources for bindless surface and sampler handles.
Bindless surface handles are expected to be pre-shifted so that the
20-bit surface state table index is in the top 20 bits of the 32-bit
handle.  This lets us avoid any extra shifts in the shader.  Bindless
sampler handles are 32-byte aligned byte offsets from general state base
address.  We use 32-byte aligned instead of 16-byte aligned to avoid
having to use more indirect messages than needed.  It means we can't
tightly pack samplers but that's probably not a big deal.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>