Fix issue with ZIP/Postal code field becoming first responder

[davidme-stripe]

Summary

• We were always setting the firstResponder to the next field when a PickerFieldView lost focus, which wasn't correct: If a user tapped a different field (like the card field), the field after the current PickerFieldView would be selected instead, and sometimes both fields would have a caret. We should instead select the next field only if a user taps the "Done" button in the accessory view.
• We wait a turn of the runloop (with DispatchQueue.main.async) before switching to the next field. This causes an animation glitch where the picker view animates out and the keyboard immediately animates up. If we switch to the next field immediately, we'll skip that animation.
• This was a workaround for a different bug, where tapping the "Postal code" field as it's becoming a "ZIP" field didn't work. This happened because the Postal code field is destroyed and a ZIP code field is created in its place.
• While switching fields, we're also incorrectly animating the size of the scrollview when the keyboard's animation duration is 0.

To fix this:

• We won't make an async call to switch fields when autoAdvancing.
• We won't autoadvance if a user taps a different cell from the PickerFieldView.
• When a text field that is about to be destroyed attempts to becomeFirstResponder, we'll store a boolean to remember that it wanted to be firstResponder. When we're destroying/recreating a Section's stackView, we'll look for views with this boolean, and if any exist, we'll manually set that field as the first responder after the new stackView is ready.
• We won't animate the size of the scrollview if the keyboard's animation duration is 0.
• This animation glitch still occurs if you go from a PickerFieldView and tap a field that is being destroyed — if I make the field the firstResponder within the animation block, it gets a caret but doesn't actually become the first responder. This appears to be a bug in UIKit, so we'll wait until after the add field animation completes before running the firstResponder.

Before	After

Motivation

MOBILESDK-1665

Testing

Existing CI tests, tested these fields in simulator (with physical keyboard) and on device:

• Klarna
• CBC in PaymentSheet
• State
• Country
• Country code in phone number

Changelog

None, too small