Adjust Windows DLL search path for Python 3.8+

[JGamache-autodesk]

Fixes #1439

Required by python/cpython#80266

[linux-foundation-easycla]

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• ✅ login: JGamache-autodesk (24cbe56, f5ab44f, 0220de7, 1dd05ef, bc93756)
• ✅ login: jstone-lucasfilm / name: Jonathan Stone (e9ba1f4, 7b4ca3f, a2d2d2d, ffbd77d, b242d6b, a2b866f)

[jstone-lucasfilm]

Apologies for the long delay on this, @JGamache-autodesk, and I wanted to follow up to see whether this pull request should move forward.

From our latest vantage point in December 2024, is this still the recommended workaround for Python versions >= 3.8 on Windows?

[JGamache-autodesk]

You will find out other similar versions of this code in USD,and many ASWF projects in either the Python install or the Python test suite.

We do add extra checks, as requested, because when installed as a Python module, the libraries end up in the folder when Python puts all libraries, which means they are already in the DLL load path. It is only when installing as a binary package that we require adding the path to the MaterialX libraries, for example, when MaterialX is packaged with USD.

[jstone-lucasfilm]

This looks good to me, thanks @JGamache-autodesk!