Contours: too many count overlays on manifold shapes

[jlampel]

The contours count overlays work well on single selected loops or non-manifold shapes such as cylindrical shapes without caps. But, when the shapes are enclosed, every edge gets a count overlay, and it becomes difficult to see the mesh.

Example where the top and bottom are open:

And then when the holes are filled:

If checking the geometry is fast enough or already happening anyway, not displaying counts in this case would be preferred. But if that's going to slow down every selection, it would also be ok to just limit the max number of count overlays to, say, five.