fix(ComboBox): handle custom value on input blur

[emyarod]

Closes #16864

This pull request fixes the handling of custom values on input blur. The changes ensure that the ComboBox correctly handles custom values again and updates the selected item accordingly. Also includes a refactoring to remove else-returns in the input blur switch block.

Changelog

Changed

• ComboBox input blur behavior

Testing / Reviewing

• visit the ComboBox story
• enable allowCustomValue
• select a preexisting value
• modify the selection to a custom value
• confirm that the previous selection is not highlighted when the component is reopened
• confirm that the new value remains in the component

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[ariellalgilmore]

LGTM!

[carbon-automation]

Hey there! v11.66.0 was just released that references this issue/PR.