Extend loop tiling utility to handle non-constant loop bounds and bounds that

Extend loop tiling utility to handle non-constant loop bounds and bounds that
are a max/min of several expressions.

- Extend loop tiling to handle non-constant loop bounds and bounds that
  are a max/min of several expressions, i.e., bounds using multi-result affine
  maps

- also fix b/120630124 as a result (the IR was in an invalid state when tiled
  loop generation failed; SSA uses were created that weren't plugged into the IR).

PiperOrigin-RevId: 224604460