Initialize and finalize Gmsh in Delaunay2D and Delaunay3D classes

[tkoyama010]

Describe the feature you would like to be added.

Links to Gmsh Documentation, Examples, or Class Definitions.

https://github.com/Deltares/pandamesh/blob/a61664fcc09d66d4d03c6c9a54b6a6d0cc188c28/pandamesh/gmsh_mesher.py#L127-L140

Pseudocode or Screenshots

    def __new__(cls, *args, **kwargs) -> "GmshMesher":
        if cls._instance is not None:
            raise RuntimeError(
                "Multiple Delaunay2D instances are not allowed. "
                "Please use del statement to clean up before creating a new instance."
            )
        cls._instance = super().__new__(cls)
        cls._instance._initialized = True
        return cls._instance

[tkoyama010]

It seems not working.
Edit: also see
https://github.com/Deltares/pandamesh/blob/a61664fcc09d66d4d03c6c9a54b6a6d0cc188c28/pandamesh/gmsh_mesher.py#L127-L140