Add missing ARIA attributes to Dropdown, Menu, and Alert

[WarLikeLaux]

Q	A
Is bugfix?	✔️
New feature?	❌
Tests added?	✔️
Breaks BC?	❌
Fixed issues

What does this PR do?

Add missing ARIA attributes: aria-disabled for disabled items in Dropdown and Menu, aria-current="page" instead of "true" in Dropdown, and default aria-label="Close" on Alert close button.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e57424b) to head (62135bb).

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #118   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity       283       284    +1     
===========================================
  Files              8         8           
  Lines            892       897    +5     
===========================================
+ Hits             892       897    +5     

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