Complete memref bound checker for arbitrary affine expressions. Handle local

variables from mod's and div's when converting to flat form.

- propagate mod, floordiv, ceildiv / local variables constraint information
  when flattening affine expressions and converting them into flat affine
  constraints; resolve multiple TODOs.
- enables memref bound checker to work with arbitrary affine expressions
- update FlatAffineConstraints API with several new methods
- test/exercise functionality mostly through -memref-bound-check
- other analyses such as dependence tests, etc. should now be able to work in the
  presence of any affine composition of add, mul, floor, ceil, mod.

PiperOrigin-RevId: 219711806