Update setuptools and fix m1 mac dev build

[MialLewis]

Description of work
This PR enables the update of setuptools within the mantid developer environments. It also fixes an issue which was causing the build and test portion of the PR/package build pipeline to fail on our M1 macs.

Following this PR, 4 unit tests still fail when ran on M1 macs. These tests will be fixed in a subsequent PR.

• Use the SUB_DIR variable when creating a mantid developer env on M1 macs to ensure an x64/86 build takes place.
• Reinstates some previously removed cmake code that circumvents the fact that recent versions of setuptools do not make use of egg-link files.
• Removed a couple of setuptools files from the cxxtest directory that are redundant.
• Added paths to python packages to the Visual Studio debug environment variables - this allows us to move past setuptools v47, where we have been stuck for a while because of Mantid doesn't work with latest setuptools on Windows #33118.

To test:

Successful build on M1 macs will be fully tested once the failing unit tests are fixed in the subsequent PR.

On Windows check that you can launch a debug build in Visual Studio:

1. Update your conda env with mamba env update -f mantid-developer-win.yml --prune (this will update your setuptools)
2. Activate your mantid-developer environment
3. Remove your build folder
4. Run e.g. cmake --preset=win-vs-2019 depending on which VS version you're using
5. Open Visual Studio using the visual-studio.bat that was generated in the build folder
6. Build the solution
7. Launch workbench and check that it works correctly.

On Linux

1. Update your mantid-developer conda env, as above
2. Clean build
3. Check that you can launch mantidworkbench

Fixes #33118

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[cailafinn]

Workbench launches properly and the code changes look good. Good to get another step closer to running our ARM macs.