Allow directories with white-spaces to be passed

[rjwignar]

This fixes #62

Summary of Changes

run-clang-format.py:

• added normalize_paths() to normalize backslashes in all elements of a list of file paths.
  • I originally considered using os.path.normpath but wasn't able to use it to normalize the backslashes
• extended split_list_arg(arg) to split arg by regex pattern (all white spaces except those preceded by a backslash) and then normalize any backslashes using normalize_paths()

Testing

The modified run-clang-format.py file was tested on Ubuntu 18.04.6 LTS using the following command:

python3 ../../clang-format-lint-action/run-clang-format.py --clang-format-executable /usr/bin/clang-format-16 --inplace "true" --exte
nsions "h,cpp,c,hlsl,hlsli" --exclude "extern include" "features/Complex\ Parallax\ Materials/Shaders/ComplexParallaxMaterials/ComplexParallaxMaterials.hlsli src/Features/DistantTreeLighting.cpp"

...to replicate as many clang-format-lint arguments used in this workflow (clang-format version, inplace, extensions, excludes), and succeeds:

Processing 2 files: features/Complex Parallax Materials/Shaders/ComplexParallaxMaterials/ComplexParallaxMaterials.hlsli, src/Features/DistantTreeLighting.cpp

This of course, requires any and all whitespaces in the filepaths to be escaped by a backslash character \, otherwise filepaths will be broken apart just as before.
E.g.:

python3 ../../clang-format-lint-action/run-clang-format.py --clang-format-executable /usr/bin/clang-format-16 --inplace "true" --extensions "h,cpp,c,hlsl,hlsli" --exclude "extern include" "features/Complex Parallax Materials/Shaders/ComplexParallaxMaterials/ComplexParallaxMaterials.hlsli src/Features/DistantTreeLighting.cpp"

will return:

Processing 4 files: features/Complex, Parallax, Materials/Shaders/ComplexParallaxMaterials/ComplexParallaxMaterials.hlsli, src/Features/DistantTreeLighting.cpp
run-clang-format.py: error: [Errno 2] No such file or directory: 'Parallax'
run-clang-format.py: error: [Errno 2] No such file or directory: 'features/Complex'
run-clang-format.py: error: [Errno 2] No such file or directory: 'Materials/Shaders/ComplexParallaxMaterials/ComplexParallaxMaterials.hlsli'

I was able to test these changes locally by testing the Python script alone, but I want to try testing these changes as a GitHub Action. Is there a way I can do this?

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Please let me know if additional changes are required.
Thank you for considering these changes.

[DoozyX]

Thanks, I am using https://github.com/DoozyX/test-action to test the action, can have the code copied from this repo as local action and test it using that one.