SearchKit - Consistently check for date field

[colemanw]

Overview

Followup from #23335, makes the logic more consistent between rendering and initializing a date widget.

Before

Fields like Contact.created_date are rendered with a datePicker as of #23335 but when loading a saved search they might not get initialized correctly in the UI.

After

Works better.

[civibot]

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[eileenmcnaughton]

test this please

[eileenmcnaughton]

unrelated fail