Add support for numpy 2.x

[jjrob]

None of what has been ported from MGET 0.8 to MGET 3.0 depends on numpy's ABI, but a lot of it depends extensively on numpy's API. We need to follow the (migration guide)[https://numpy.org/devdocs/numpy_2_0_migration_guide.html] and also check the 2.0 (release notes)[https://numpy.org/devdocs/release/2.0.0-notes.html]. Mostly we need to adjust MGET's code to changes in numpy's namespace.

Some parts of MGET that have not been ported yet, such as the Cayula-Cornillon front detection algorithm, do depend on the ABI. These will require changes to C/C++ code. We'll handle those later as part of porting them.