feat: Unify Alert and Banner under a single Banner component with new designs

[pedroalves0]

Short description

Recently, in the "Downgrade" squad, the team put together new designs that included banners that didn't match the current version of the banner component in Reactist. The design team has since updated the design system product library, and we're now ready on the frontend side to implement those changes.

Although not strictly necessary, we're taking this opportunity to unify the Alert and the Banner components under a single component, as in the design system library, there's only a "Banner" component, and both have similar use cases.

One caveat is that the banner variant with an image is not responsive. I tried to implement a CSS-only solution but wasn't successful; we might have to resort to using JavaScript. That said, there aren't any instances of the new variant in our apps, so I propose revisiting this limitation in the future, if necessary.

Figma ref
Twist: Banner Component

PR Checklist

• Added tests for bugs / new features
• Updated docs (storybooks, readme)
• Executed npm run validate and made sure no errors / warnings were shown
• Described changes in CHANGELOG.md
• Bumped version in package.json and package-lock.json (npm --no-git-tag-version version <major|minor|patch>) ref
• Reviewed and approved Chromatic visual regression tests in CI

📸 Demo

CleanShot.2024-12-26.at.15.59.56.mp4

Versioning

Major - Breaking change as the Banner API is changing and Alert is removed.

[Bloomca]

Left a few small comments, looks good!