refactor: rename dropdownContentRole to ariaRole

[mxschll]

Description

• This PR refactors the dropdownContentRole prop of the Dropdown component to be named ariaRole aligning its API with Flashbar
• Introduces the ariaLabel prop

Related

[Quip proposal: RGJgABPXohP8]

How has this been tested?

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 97.35%. Comparing base (87a3e47) to head (2f4804f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4248   +/-   ##
=======================================
  Coverage   97.35%   97.35%           
=======================================
  Files         888      888           
  Lines       26031    26031           
  Branches     9411     9410    -1     
=======================================
  Hits        25343    25343           
- Misses        641      682   +41     
+ Partials       47        6   -41     

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[mxschll]

That's on the div, so it stays role :)