Add convenience function to transform multiple point inputs into the same shape

For function dealing with point input like `interp_points`, we should support various input types and convert on-the-fly:
- `PointCloud`,
- `gpd.GeoDataFrame` containing only points,
- `tuple[ArrayLike, ArrayLike]`,
- `ArrayLike[tuple[Number, Number]]`,
- `NDArray` with either shape Nx2 or 2xN,
- and exceptions for a single point input.