Merging branch 'm.i20a'  into 'main'.

See merge request !2730

Merging branch 'm.i20'  into 'main'.

See merge request !2729

Merging branch 'm.i875'  into 'main'.

See merge request !2728

Merging branch 'a.rmCpp20'  into 'main'.

See merge request !2727

Avoid using C++20 features to keep the libraries maintainable on older systems.

Merging branch 'm.i972'  into 'main'.

See merge request !2726

Merging branch 'a.newNumpyInterface_rmNumpy'  into 'main'.

The Numpy C-API is removed from the build mechanism.
Numpy Python package is needed only for tests.

* Removed the references to the Numpy C-API from the `PyCore` module.
* Removed SWIG include file `Wrap/Swig/numpy.i` and updated `Wrap/Swig/commons.i`.
* Updated the tests.
* Updated SWIG-produced C++ wrappers.


See merge request !2724