Dead code cleanup and improved consistency of code

[Mil4n0r]

Checklist
(Check off all the items before submitting)

• Build process is done without errors. All tests pass in the /lib directory.
• Self-reviewed the code before submitting.
• Meets accessibility standards.
• Added/updated documentation to /website as needed.
• Added/updated tests as needed.

We still had plenty of files related to old theming strategy which were no longer useful, so I have done an overall cleanup, also taking the opportunity to increase the consistency of our code conventions (using arrow functions over normal functions when possible, removing unneeded empty wrappers, etc.), removing unsupported characters and fixed a few minor typos or missing texts in the doc.

I still have a few more changes that I would like to add such as replacing all the "rem", "em" and "px" with the correct css tokens and redoing the spacing logic for those components that have it dynamic, but that's a bigger task that can wait.