Add support for numpy 2

[Ericgig]

Description
Add support for the up comming numpy v2:

• Allows qutip to be compiled with numpy 2, and pass tests.
• Test that binaries compiled with numpy 2 are compatible with numpy 1 at runtime.

I did not update the requirement yet, it must be installed in --no-build-isolation.
When it's officially released, we will need to update pyproject.toml and setup.cfg, and possibly add test for np2 on windows and mac.

Here are the changes that affect us:

• np.array(.., copy=False) no longer mean copy only if needed. copy=None was added for that.
• np.trapz was replaced by np.trapezoid. Since there are no overlaps, I opted to use scipy.integrate.trapezoid instead.
• np.array(1, np.int32) * 2**33 will enforce the integer type and overflow.
• Py_intptr_t from python.h is no longer available through numpy cython interface.

[coveralls]

coverage: 86.293% (+0.03%) from 86.267%
when pulling cbd9f91 on Ericgig:misc.np2
into 4acc9f1 on qutip:master.

[hodgestar]

Woot for starting to get things ready for numpy 2. Did a quick review of the changes so far. Most look good.

[hodgestar]

Numpy is maintaining a list of project versions that support numpy 2 -- numpy/numpy#26191. They're waiting of downstream packages to be ready before release. We could add ourselves there if we liked.

[eendebakpt]

Numpy 2.0 is scheduled to be released June 16th (see numpy/numpy#24300 (comment))