[WIP] migrate cmake to use FindPython instead of FindPythonInterp+FindPythonLibs

[rvianello]

What does this implement/fix? Explain your changes.

With cmake version 3.27.7 the following warning is produced at configuration time:

[cmake] CMake Warning (dev) at CMakeLists.txt:302 (find_package):
[cmake]   Policy CMP0148 is not set: The FindPythonInterp and FindPythonLibs modules
[cmake]   are removed.  Run "cmake --help-policy CMP0148" for policy details.  Use
[cmake]   the cmake_policy command to set the policy and suppress this warning.

cmake --help-policy CMP0148 produces the following output:

CMP0148
-------

.. versionadded:: 3.27

The ``FindPythonInterp`` and ``FindPythonLibs`` modules are removed.

These modules have been deprecated since CMake 3.12.
CMake 3.27 and above prefer to not provide the modules.
This policy provides compatibility for projects that have not been
ported away from them.

Projects using the ``FindPythonInterp`` and/or ``FindPythonLibs``
modules should be updated to use one of their replacements:

* ``FindPython3``
* ``FindPython2``
* ``FindPython``

The ``OLD`` behavior of this policy is for ``find_package(PythonInterp)``
and ``find_package(PythonLibs)`` to load the deprecated modules.  The ``NEW``
behavior is for uses of the modules to fail as if they do not exist.

This policy was introduced in CMake version 3.27.  CMake version
3.27.7 warns when the policy is not set and uses ``OLD`` behavior.
Use the ``cmake_policy()`` command to set it to ``OLD`` or ``NEW``
explicitly.

.. note::
  The ``OLD`` behavior of a policy is
  ``deprecated by definition``
  and may be removed in a future version of CMake.

This PR migrates the RDKit cmake files to use FindPython.

Any other comments?

The changes are for the most part relatively simple, the part I'm less confident in is the replacement of PYTHON_ADD_MODULE with Python_add_library in Code/cmake/Modules/RDKitUtils.cmake, that I was at the moment only able to test on Linux.

[greglandrum]

@rvianello this is still marked WIP. Is it ready for review?

[rvianello]

@greglandrum the changes to the cmake scripts should be mostly complete, but configuration fails for the windows and macos CI builds. I'll try investigating/troubleshooting these issues first.