refactor: use native padStart() in padLeftZeros utility

[TrevorBurnham]

Description

This PR replaces a while loop with padStart for cleaner, more idiomatic code. The padStart method has been widely supported for several years now.

How has this been tested?

This utility function has extensive unit test coverage.

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 97.17%. Comparing base (4129df4) to head (ae40994).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4202      +/-   ##
==========================================
- Coverage   97.17%   97.17%   -0.01%     
==========================================
  Files         882      882              
  Lines       25826    25824       -2     
  Branches     9333     9333              
==========================================
- Hits        25097    25095       -2     
  Misses        682      682              
  Partials       47       47              

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