WIP | fix: stopped combobox's onChange throwing undefined when selected item is clicked again and fixed keyboard interaction

[Gururajj77]

Closes #18286
Closes #18386

18226 issue: stops the onChange handler from firing with undefined when the same item is clicked. Now it does not fire onChange handler when the selected item is clicked again.

Second: The keyboard interaction would fire 2 onChange handlers, one with previously selected value and one with the new selected value.

Changelog

Changed

• modified the onStateChange to include a check for being undefined:
  newSelectedItem !== undefined

Removed

• if (allowCustomValue && isOpen && inputValue) {
  onChange({ selectedItem, inputValue });
  }

Removed this condition as this was firing the onChange with previous selected value when the combobox is interacted with keyboard

Testing / Reviewing

• Open the test story
• keep the console open
• select item '2' by using keyboard
• see that console has a log:
  Parent onChange called with: 2

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