[Tidy] Replace RadioItems and Checklist

[huong-li-nguyen]

Description

• Add new Bootstrap CSS file with RadioItems and Checklist added
• Remove all custom CSS related to these two components
• Refactor RadioItems and Checklist to use semantically correct Fieldset and Legend, for context see: https://accessibility.blog.gov.uk/2016/07/22/using-the-fieldset-and-legend-elements/
• Remove redundant input-container class from selectors to consolidate gaps
• Add another unit test for Card (for context: I broke it during this PR at some point, but there was no test covering it)

TO DO

• Tests are currently being fixed here: https://github.com/mckinsey/vizro-qa/pull/82
• Minor refinements are still coming but that won't affect the core changes here, so this PR can be reviewed already

Screenshot

Run features demo dashboard:

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[nadijagraca]

LGTM.I like the use of html.Fieldset. 🚀

[maxschulz-COL]

⭐ LGTM!