fix: update compareItems type in MultiSelect

[adamalston]

Closes #18199

Updated compareItems type in MultiSelect.

Changelog

New

• Added defaultCompareItems tests.

Changed

• Updated compareItems type in MultiSelect.

Testing / Reviewing

• Run the test that was added.
• Use compareItems in a TypeScript file similar to the reproduction in the issue and check for errors.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.02%. Comparing base (494ab2e) to head (fe93944).
Report is 13 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #18599   +/-   ##
=======================================
  Coverage   84.02%   84.02%           
=======================================
  Files         408      408           
  Lines       14494    14494           
  Branches     4726     4676   -50     
=======================================
  Hits        12178    12178           
  Misses       2150     2150           
  Partials      166      166           

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[tay1orjones]

One question but nothing to hold up a merge. Thanks for this contribution!

[tay1orjones]

Are we losing some strictness here by moving the items from ItemType to string?

[adamalston]

Wasn't that the problem, that the items had type ItemType instead of string? Aren't the items going through itemToString before they go to the comparison function?