Tests failing for numpy v>=2.0

[kkappler]

Currently working on some patches for numpy version 2.0 (deprecation of np.complex_, np.float_, np.unicode_)

I'm fine with making these changes, but do we need tests to make sure that we don't break compatability with numpy <2.0?

Options to be robust to this:

• The numpy version should be pinned in mt_metadata

I note also that the hassle we had with the windows default integer being 32bit should be fixed in numpy 2+

[kkappler]

fixed by PR 218