[EuiAspectRatio] Remove sass and replace with inline styles

[snide]

Summary

Converts EuiApsectRatio to use the new aspect-ratio css property https://caniuse.com/mdn-css_properties_aspect-ratio

This removed a bit of the css, and since this has no themable elements, it felt best to just convert it completely to inline styles.

Checklist

• [ ] Checked in both light and dark modes
• Checked in mobile
• Checked in Chrome, Safari, Edge, and Firefox
• [ ] Props have proper autodocs and playground toggles
• Added documentation
• Checked Code Sandbox works for any docs examples
• Added or updated jest and cypress tests
• Checked for breaking changes and labeled appropriately
• Checked for accessibility including keyboard-only and screenreader modes
• Updated the Figma library counterpart
• A changelog entry exists and is marked appropriately

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5818/

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5818/

[cchaos]

LGTM! I checked a lot of our direct uses in our docs in all three browsers. Yay for plain CSS and yay for reducing div count!

If you update from main, I think CI will pass

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5818/