nir: Add new system values and intrinsics for dealing with CL work offsets

nir: Add new system values and intrinsics for dealing with CL work offsets

New intrinsics are added for global invocation IDs and work group IDs to
deal with offsets in both. The only one of these that needs a system value
is global invocation offset, for CL's get_global_offset().

Note that CL requires very large work group sizes, so these intrinsics
are modified to be able to use 64bit values, for 64bit SPIR-V.

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5891>