nir/idiv_const: intel/compiler: Unify integer constant division optimizations

Over a year ago in a comment in !17475 (closed) I mentioned that I was working on this... them promptly forgot. 🤦

The first few commits move all integer division by a constant optimizations from algebraic to nir_opt_idiv_const. The next couple commits try to improve those optimizations, and the last couple are small tweaks to the Intel driver.

There are a couple different modifications of nir_opt_idiv_const in https://gitlab.freedesktop.org/idr/mesa/-/tree/wip/integer-divide2.