feat: Add filtering to button dropdown

[avinashbot]

Description

Button dropdown action filtering implemented a similar way to select/multiselect filtering. The big underlying change is that filtering requires the use of aria-activedescendant rather than simply moving focus from item to item. So most of the internal changes are about disabling focusing logic when filtering is active, so that the real focus can stay on the input (and "accessibility" focus can move around using aria-activedescendant).

Rel: AWSUI-61960 (Chorus: qodG8KXdJXXk)

How has this been tested?

Updated unit tests, a bit of manual accessibility testing, but more validation with other screen readers is needed.

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 97.60%. Comparing base (902b5ad) to head (f0e34d7).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4637      +/-   ##
==========================================
+ Coverage   97.57%   97.60%   +0.02%     
==========================================
  Files         948      950       +2     
  Lines       30489    30612     +123     
  Branches    11148    11216      +68     
==========================================
+ Hits        29749    29878     +129     
+ Misses        733      688      -45     
- Partials        7       46      +39     

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[pan-kot]

All these tests are technically possible to run from the component level: render button dropdown with certain items, set filtering - check the actual rendered items. Should we do this instead of testing the helper directly? This can give us better real coverage, as it not only ensures that the helper works, but also that it is used correctly by the component.

[pan-kot]

Why did we add this test? Is that also the expected behaviour? I find it strange that we still render a link when the item renderer is overridden.

[amanabiy]

Did the behavior change here? or we don't need the comment?

[amanabiy]

Same, Did the behavior change here? or we don't need the comment?

[amanabiy]

Should we use usePrevious here?

const prevFilteringValue = usePrevious(filteringValue);