feat: make extensible `Quantity` component

[lauthieb]

Changes description

Closes #1356

As we need to make it extensible without making breaking changes, I propose to add a new prop called fullWidth (boolean by default === 'false').

For your information, in Figma, there's no prop (variant) because the behavior is like this: . That was I think the best thing to reproduce this behavior is to set a full width based on the quantity's parent.

Checklist

• [x] Make sure you are requesting to pull a topic/feature/bugfix branch. Please, don't request directly from your main!
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• [x] Check your code additions will fail neither code linting checks.
• [x] I have reviewed the submitted code.
• [x] I have tested on related showcases.
• [x] If it includes design changes, please ask for a review design-system-core-team-design GitHub team.

Does this introduce a breaking change?

• No