fix: Cache dropdown's overflow parents for better jsdom performance

[jperals]

Description

getOverflowParents is expensive on testing environments because we are calling getComputedStyle on every element in the parent chain and Jest does not yet incorporate a version of jsdom that includes this fix. This causes some packages to have test timeouts after #1555.

This PR handles this by caching the result of getOverflowParents in the dropdown component. Note that it does not cache their dimensions, which will still be recalculated as necessary.

Ticket: AWSUI-22613

How has this been tested?

• Successful dry-run build to previously failing package
• Successfully ran tests in previously failing package, and observed that the run time is reduced significantly (~3x).

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 lines are covered by tests ✅

Comparison is base (9369a80) 94.19% compared to head (5cfd326) 94.19%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1669      +/-   ##
==========================================
- Coverage   94.19%   94.19%   -0.01%     
==========================================
  Files         650      650              
  Lines       17523    17531       +8     
  Branches     5769     5772       +3     
==========================================
+ Hits        16506    16513       +7     
- Misses        948      949       +1     
  Partials       69       69              

Files	Coverage Δ
...ternal/components/dropdown/dropdown-fit-handler.ts	94.57% <100.00%> (ø)
src/internal/components/dropdown/index.tsx	91.81% <100.00%> (+0.50%)	⬆️
src/internal/utils/scrollable-containers.ts	88.46% <100.00%> (-0.83%)	⬇️

... and 1 file with indirect coverage changes

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[jperals]

Closing in favor of #1679