chore: Styling v2 utils, part 1

[pan-kot]

Description

Introducing the first set of Style API v2 utils, see QUIP [RF7BAXdY9QZb] and [3LQzAqi0WIlT]. These utils were originally added in the POC implementation (#4577), but here I am adding them as a standalone change, covered with a dedicated test page (to be covered with screenshot tests). Compared to the POC, I introduced a few small ergonomics/naming changes.

Once this one is merged, I will follow it up by a few more similar PRs - introducing shared token groups (surface, focus outline, etc.), and a mechanism to extract style tokens documentation.

How has this been tested?

• New test page, to be covered with a screenshot test

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.59%. Comparing base (4d2e475) to head (b6f5185).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4720      +/-   ##
==========================================
- Coverage   97.59%   97.59%   -0.01%     
==========================================
  Files         950      950              
  Lines       30664    30690      +26     
  Branches    11242    11255      +13     
==========================================
+ Hits        29928    29953      +25     
- Misses        689      690       +1     
  Partials       47       47              

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