Support for Numpy 2

[jakelishman]

Numpy are currently aiming to release Numpy 2 around the end of the December or in January (ref: numpy/numpy#24300). This is a tracking issue for various things we may need to do in order to support the new major release.

I'm likely to update this list as I/we find more things.

Tasks

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1. Incompatibility with Numpy 1.25 #10305
   bug +1
2. Remove use of dtype aliases to be removed in Numpy 2 #10890
   Changelog: None stable backport potential +2
3. Remove use of singleton aliases removed in Numpy 2 #10891
   Changelog: None stable backport potential +2
4. Replace use of numpy.lib.scimath with preferred numpy.emath #10892
   Changelog: None stable backport potential +2
5. Fix casting rules changing in Numpy 2 #10897
   Changelog: None mod: quantum info type: qa +3
6. Verify usage of Numpy C API via PyO3 / Rust's numpy crate
7. Test against Numpy 2.0rc once released
8. Release pin on numpy<2 once we're building/testing against it (even as rc)

I'm trying to get most of the deprecated usage squashed now. If we let a few more bits of deprecated behaviour slip in between now and the Numpy 2 release, it's not the end of the world, and hopefully the subtasks of this issue will point us to what needs to be fixed.