fix: Handle multiple intersection changes in a single callback

[just-boris]

Description

Fixing a bug where useIntersectionObserver only checks the first change entry instead of the latest.

Check the docs: https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API

The list of entries received by the callback includes one IntersectionObserverEntry object for each threshold-crossing event — multiple entries can be received at a time, either from multiple targets or from a single target crossing multiple thresholds in a short amount of time. The entries are dispatched using a queue, so they should be ordered by the time they were generated, but you should preferably use IntersectionObserverEntry.time to correctly order them.

Related links, issue #, if available: n/a

How has this been tested?

• Manually with the changes in chore: Move more app layout code into the widgetized part #3721 which reproduced the issue
• Added more unit tests

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 97.01%. Comparing base (8d13105) to head (d5d6553).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3747    +/-   ##
========================================
  Coverage   97.01%   97.01%            
========================================
  Files         825      825            
  Lines       23946    23950     +4     
  Branches     8426     7997   -429     
========================================
+ Hits        23231    23235     +4     
- Misses        666      709    +43     
+ Partials       49        6    -43     

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