Forms: use a dropdown selector to list eligible users for notifications (#45634)

* Use dropdown selector for notification recipients

To make it easier to select users in the form notification settings, I'm
using the FormTokenField dropdown selector variation, which will list
all the eligible users we can send notifications to.

* changelog

Author: vianasw

projects/packages/forms/changelog/update-form-notification-recipients-input

@@ -0,0 +1,4 @@
+Significance: minor
+Type: changed
+
+Forms: use a dropdown selector to list eligible users to receive form notifications.

projects/packages/forms/src/blocks/contact-form/components/notifications-settings.js

@@ -136,6 +136,8 @@ const NotificationsSettings = ( {
 							} }
 							__nextHasNoMarginBottom={ true }
 							__next40pxDefaultSize={ true }
+							__experimentalExpandOnFocus={ true }
+							__experimentalAutoSelectFirstMatch={ true }
 						/>
 					</>
 				) }