refactor: ThicknessFilterKinds location and improves converter XML documentation

[United600]

• Moves the ThicknessFilterKinds enum to a new file
• Updates ThicknessFilterKinds to use binary enum literals
• Updates ThicknessFiltersConverter XML documentation code block language values

As of Visual Studio 18.3, Roslyn now provides syntax highlighting for XML code blocks.

Before	After

PS: For some reason, they used a different tag than Markdown 😢.

[huynhsontung]

For some reason, they used a different tag than Markdown 😢

Booo 😞