refactor(button): remove use of enum

Related to #427 (closed)

What does this MR do and why?

This MR improves DX by removing the use of variant enums for buttons.

The v3 button was developed the same way we did in v2 but it's less convenient because :

• you have to import the enum in .ts files to make the enum available in html files
• we had inconsistent naming of types : buttonTypeV3 buttonTypeEnumV3 buttonTypeV3Enum
• longer

This MR also removes the default type and mark the input variant as required

Still gives autocompletion :

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

How to set up and validate locally (or on alpha)

Make also sure that storybook works fine

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MR acceptance checklist

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• For the code that this change impacts, I believe that the automated tests validate functionality that is highly important to users. If the existing automated tests do not cover this functionality, I have added the necessary additional tests or I have added an issue to describe the automation testing gap and linked it to this MR.
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