feat: add aria-label prop support for DatePicker

[martijnrusschen]

Adds support for aria-label prop to the DatePicker component, allowing users to provide accessible labels for screen readers without needing a visible label element on the page.

The prop can be used with either the standard HTML attribute name (aria-label) or the camelCase prop name (ariaLabel), following the same pattern as existing aria props like ariaLabelledBy.

Fixes #5981

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.21%. Comparing base (5d228d3) to head (dbfd2d3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6057   +/-   ##
=======================================
  Coverage   99.21%   99.21%           
=======================================
  Files          30       30           
  Lines        3584     3586    +2     
  Branches     1516     1534   +18     
=======================================
+ Hits         3556     3558    +2     
  Misses         27       27           
  Partials        1        1           

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