Windows MapScript for Conda build

[hobu]

Follow up to #7102 to add MapScript builds as well on all three platforms

[geographika]

Thanks @hobu !

Note to self: shell-paths for converting slashes in paths dependent on OS.

[rouault]

It is weird that we have to explicitly specify SWIG_EXECUTABLE. We don't need to do that for GDAL builds

[hobu]

This could probably be removed. It was in the mapserver feedstock and I carried it along from there.

[rouault]

This could probably be removed

indeed: #7109

[hobu]

Note to self: shell-paths for converting slashes in paths dependent on OS.

IMO the Python MapScript install stuff should be refactored to use "modern" Python packaging installation stuff instead of hand copying files around to paths. Some of the items that would entail include:

• A proper MANIFEST.in file to describe the examples and data and such that should be installed with Python MapScript
• Use pyproject.toml for all of the package metadata (readme, version, etc)
• Proper rpath'ing to get rid of MAPSERVER_DLL_PATH (and the rest of the dirty hackery in __init__.py)

[geographika]

@hobu - there are definitely some improvements that can be made such as a move to a .toml file, but I'm not sure if there is a "clean" way when building with a combination of SWIG, CMake, and Python packaging.

Setting MAPSERVER_DLL_PATH is required on Windows to allow the MapServer DLLs to be referenced from MapScript - see #6101.
Including the mapserver/bin folder on the system PATH no longer works since Python 3.8.

GDAL also relies on several path manipulations in https://github.com/rouault/gdal/blob/master/swig/python/osgeo/__init__.py

Copying files with CMake is required to gather the files from the source repository such as tests so they can be alongside the SWIG generated .py file and a .pyd file and added to the wheel.