TriangulatorInterface::MeshedHole cannot have multiple holes from a mesh currently

[YaqiWang]

When constructing TriangulatorInterface::MeshedHole with a mesh that has multiple disconnected regions, we will hit an error like

MeshedHole found 6 clockwise boundaries and cannot choose one!

This error can be triggered with a MOOSE mesh generator XYDelaunayGenerator where a mesh for a hole may have multiple holes. Users would expect the mesh generator to handle this. We may need to add a new static function in MeshedHole that takes a mesh and returns a vector of MeshedHole. Tag @roystgnr