Detect non matching edges between two sets of two tets

[GiudGiud]

Reason

When splitting hexes, there are two choices for how to split a quad face into two triangles to form tet elements. If one hex pick one option, and the other picks another, the tets will not share the vertex.

Design

Add to MeshDiagnosticsGenerator

Impact

Will help us evaluate the effectiveness / correctness of element conversion techniques