Polyfill smooth scrolling for Safari

What does this MR do and why?

This polyfills Safari browsers to enable programmatic smooth scrolling on elements with overflow: hidden.

Implemented behind the fix_safari_smooth_scroll feature flag.

Addresses #369237 (closed).

Screenshots or screen recordings

Before	After
TODO	TODO

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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Related to #369237 (closed)