RG-2661 Replace the old loader with the new one

[Hypnosphi]

RG-2661 Replace the old loader with the new one

[Copilot]

Pull Request Overview

This PR introduces a new squares-based loader animation as an alternative to the existing loader implementation. The changes add a new visual style for the loader component while maintaining backward compatibility with the original implementation.

Key Changes:

• Added a new squares prop to the Loader component to enable the new animation style
• Implemented CSS animations for three rotating squares with color transitions
• Created a new Storybook story to showcase the squares loader variant

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/loader/loader.tsx	Added squares prop and conditional rendering logic for the new loader animation
src/loader/loader.stories.tsx	Added new story for the squares loader and reorganized screenshot parameters
src/loader/loader.css	Implemented CSS animations and styles for the squares loader variant
packages/screenshots/testplane/firefox/components/loader/squares/*.png	Added Firefox screenshot tests for squares loader
packages/screenshots/testplane/chrome/components/loader/squares/*.png	Added Chrome screenshot tests for squares loader

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