Utility function to promote coord dtype

[HGWright]

📰 Custom Issue

This should be part of the equalise_cubes operation. This should add a function that can operate as a parameter of equalise_cubes. We should aim to promote the dtype of coords so that the dtype matches.

For Example is we had a coord of int32 and another of float32 before this operation, we should end up with both coords being float32 after.