DateTimePicker: fix onChange callback check so that it also works inside iframes

[ciampo]

What?

Fixes #54378
Inspired by #54643

Improve internal check in DateTimePicker so that the onChange callback fires even when the picker is rendered inside an iframe.

Why?

Making the component more robust by not assuming (in the instanceof check) that it always going to be rendered in the root window.

How?

By grabbing the HTMLInputElement value from the event target's owner window.

Testing Instructions

1. Apply the following diff:

Click to expand

diff --git a/packages/block-library/src/button/edit.js b/packages/block-library/src/button/edit.js
index 0c1892c6e4..4dbb6fcda3 100644
--- a/packages/block-library/src/button/edit.js
+++ b/packages/block-library/src/button/edit.js
@@ -15,6 +15,7 @@ import {
 	TextControl,
 	ToolbarButton,
 	Popover,
+	TimePicker,
 } from '@wordpress/components';
 import {
 	AlignmentControl,
@@ -170,6 +171,10 @@ function ButtonEdit( props ) {
 
 	return (
 		<>
+			<TimePicker
+				currentDate={ new Date() }
+				onChange={ ( date ) => console.log( 'logging here: ', date ) }
+			/>
 			<div
 				{ ...blockProps }
 				className={ classnames( blockProps.className, {

2. In the editor, add a "Buttons" block
3. Interact with the datetime picker fields, and make sure that the console logs are printed when changing every input field in the component
4. As a comparison, apply the same diff on trunk and check that only the month dropdown causes the console log to fite
5. Additionally, check that the callback fires as expected also in Storybook (this can be seen by checking the "actions" tab)

[bangank36]

Working well! ownerDocument.defaultView is good use
All input changes fire correct data on both Storybook and Editor

Editor	Storybook
Kapture.2023-09-20.at.22.48.24.mp4	Kapture.2023-09-20.at.22.51.34.mp4

[github-actions]

Flaky tests detected in b551a18.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/6250831673
📝 Reported issues:

• [Flaky Test] should load multiple block stylesheets in iframe #35394 in specs/editor/plugins/iframed-multiple-block-stylesheets.test.js
• [Flaky Test] should partially select with shift + click (@webkit) #53524 in /test/e2e/specs/editor/various/multi-block-selection.spec.js

[aaronrobertshaw]

This works well for me 👍

✅ Could replicate original issue on trunk
✅ This PR correctly fires onChange callback for all inputs when inside an iframe
✅ Tested well in the editor and the Storybook

Nice work @ciampo!

[mikachan]

I just cherry-picked this PR to the release/16.7 branch to get it included in the next release: e38d246