anv: Use 3DSTATE_CONSTANT_ALL when possible.

anv: Use 3DSTATE_CONSTANT_ALL when possible.

Use this new instruction introduced in Gen12. The instruction itself is
smaller, and it also allows us to emit a single instruction to all
stages that have the same push constant buffers (e.g. when they don't
have constant buffers).

There's one restriction to use this instruction, though: the length
field is only 5 bits long, so we need to check whether we can use it,
and fallback to the old 3DSTATE_CONSTANT_XS if that field is >= 32.

v2:
 - Rebased on top of the lasted changes from Jason.
 - Added review suggestions by Caio.
 - Removed struct push_bos and merged some code into
 anv_nir_compute_push_layout().

v3:
 - Remove code churn due to gen8+ workaround in
 anv_nir_compute_push_layout(). This code has been removed in an earlier
 commit, and implemented in cmd_buffer_emit_push_constant().

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>