ac/nir: Add new pass to lower intrinsics to shader args.

ac/nir: Add new pass to lower intrinsics to shader args.

This is beneficial for intrinsics that do an algebraic
instruction such as bitfield extract on shader arguments,
because it allows NIR to be aware of these instructions and
optimize them together with other algebraic instructions in
the shader.

Currently, just handle subgroup_id and num_subgroups intrinsics.
More will be added here in the future.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24005>