intel/compiler: Create a struct to hold SIMD selection state

intel/compiler: Create a struct to hold SIMD selection state

This is a preparation to decouple the storage of what SIMDs
compiled/spilled from the cs_prog_data.  This will allow reuse
of SIMD selection code by Bindless Shaders.

And since we have a struct now, move the error array there so
reduce the boilerplate of the users.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Ivan Briano <ivan.briano@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19601>