interpdn / SciPy>=1.15

[prisae]

• Make it compatible with scipy>=1.5
• Check if interpnd._ndim_coords_from_arrays is still needed or not.
  (Edit: still needed)
• Check if https://github.com/emsig/emg3d/blob/main/emg3d/maps.py#L335-L336 can be dealt with
  (Edit: defer to new PR/issue, is not really related)
• Really odd test failure here: https://github.com/emsig/emg3d/blob/main/tests/test_meshes.py#L316 - find out why
  (Edit: definitely not related to this PR, but needs solving anyhow)

Closes #352