This PR adds support for case splitting on `match`-expressions with
overlapping patterns to the `grind` tactic. `grind` can now solve
examples such as:
```
inductive S where
| mk1 (n : Nat)
| mk2 (n : Nat) (s : S)
| mk3 (n : Bool)
| mk4 (s1 s2 : S)
def g (x y : S) :=
match x, y with
| .mk1 a, _ => a + 2
| _, .mk2 1 (.mk4 _ _) => 3
| .mk3 _, .mk4 _ _ => 4
| _, _ => 5
example : g a b > 1 := by
grind [g.eq_def]
```
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