[MLIR] Generalize detecting mods during slice computing

[MLIR] Generalize detecting mods during slice computing

During slice computation of affine loop fusion, detect one id as the mod
of another id w.r.t a constant in a more generic way. Restrictions on
co-efficients of the ids is removed. Also, information from the
previously calculated ids is used for simplification of affine
expressions, e.g.,

If `id1` = `id2`,
  `id_n - divisor * id_q - id_r + id1 - id2 = 0`, is simplified to:
  `id_n - divisor * id_q - id_r = 0`.

If `c` is a non-zero integer,
  `c*id_n - c*divisor * id_q - c*id_r = 0`, is simplified to:
  `id_n - divisor * id_q - id_r = 0`.

Reviewed By: bondhugula, ayzhuang

Differential Revision: https://reviews.llvm.org/D104614