Control ArrowUp and ArrowDown keys for Dropdown

[cknabe]

Closes #18277

Disallows ArrowUp if the first item is selected.
Disallows ArrowDown if the last item is selected.
Allows all key-presses when the Dropdown is open
Allows all key-presses that are not ArrowUp or ArrowDown

Testing / Reviewing

1. Load the Dropdown component in the storybook
2. Press arrow up and select the first item
3. Press arrow up and see Dropdown does not open
4. Press arrow down and select the last item
5. Press arrow down and see Dropdown does not open
6. Press arrow up and select some item in the middle
7. Press arrow down/up and see Dropdown opens

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[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.17%. Comparing base (e973f28) to head (6489e55).

Files with missing lines	Patch %	Lines
...ackages/react/src/components/Dropdown/Dropdown.tsx	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18324      +/-   ##
==========================================
- Coverage   84.17%   84.17%   -0.01%     
==========================================
  Files         408      408              
  Lines       14435    14441       +6     
  Branches     4690     4696       +6     
==========================================
+ Hits        12150    12155       +5     
- Misses       2121     2122       +1     
  Partials      164      164              

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