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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[annawen1]

Hi @cknabe, trying to follow the ticket linked in the corresponding bug issue - are the rules listed in your PR description coming from another issue?

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

[cknabe]

@annawen1 No, #18277 states this:

The closed default & fluid dropdown input should not open when the user presses the Up arrow key, as unlike the combobox, there is no ability to wrap around the options list (i.e., pressing the Up arrow at the top of the open list does nothing).

This PR causes the Dropdown to not open when the user is at the top selection and they press the up arrow key.
When the user is at the bottom selection and presses the down arrow key, it also does not open.

[annawen1]

@annawen1 No, #18277 states this:

The closed default & fluid dropdown input should not open when the user presses the Up arrow key, as unlike the combobox, there is no ability to wrap around the options list (i.e., pressing the Up arrow at the top of the open list does nothing).

This PR causes the Dropdown to not open when the user is at the top selection and they press the up arrow key. When the user is at the bottom selection and presses the down arrow key, it also does not open.

I see, I had understood the issue to mean that the Dropdown should not open at all on arrowUp regardless of which item is selected... @Kritvi-bhatia17 could you clarify? And on the disabling of opening Dropdown on arrowDown when last item is selected?