This PR is initially motivated by noticing `Lean.Grind.Preorder.toLE`
appearing in long Mathlib typeclass searches; this change will prevent
these searches. These changes are also helpful preparation for
potentially dropping the custom `Lean.Grind.*` typeclasses, and unifying
with the new typeclasses introduced in #9729.
This PR implements support for the heterogeneous `(k : Nat) * (a : R)`
in ordered modules. Example:
```lean
variable (R : Type u) [IntModule R] [LinearOrder R] [IntModule.IsOrdered R]
example (x y z : R) (hx : x ≤ 3 * y) (h2 : y ≤ 2 * z) (h3 : x ≥ 6 * z) : x = 3 * y := by
grind
example (x y z : Int) (h1 : 2 * x < 3 * y) (h2 : -4 * x + 2 * z < 0) (h3 : x * y < 5) : ¬ 12*y - 4* z < 0 := by
grind
```
