DOC: Updated documentation for squeeze

Improve clarity by replacing terms like "single-dimensional" and
"singleton dimension" with "axes of length one"

DEP: Deprecate `numpy.dual`.

This solution is related to the issue #15986. I also made a change to the newer string formatting.
Uses NameError, which prints nicer, and is actually the more correct error type.

Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

Add a deprecation warning in the `numpy.dual` module, and
remove the use of `numpy.dual` from the few places where it
is used in the numpy code.

Add missing closing brackets, script to generate the list in the PR gh-16051.

As numpy is Python 3 only, these import statements are now unnecessary
and don't alter runtime behavior.

* ported the refguide_check module from SciPy for usage
in NumPy docstring execution/ verification; added the
refguide_check run to Azure Mac OS CI

* adjusted NumPy docstrings such that refguide_check passes

Fixes GH-12271

Tests verify that everything in ``dir(numpy)`` either has ``__module__`` set to
``'numpy'``, or appears in an explicit whitelist of undocumented functions and
exported bulitins. These should eventually be documented or removed.

I also identified a handful of functions for which I had accidentally not setup
dispatch for with ``__array_function__`` before, because they were listed under
"ndarray methods" in ``_add_newdocs.py``. I guess that should be a lesson in
trusting code comments :).