StripeReview improvements

Problem/Motivation

This addition addresses several checkout flow issues and edge cases that can occur during the Stripe payment process.

Proposed resolution

1. Auto-redirect for already completed payments. Check $intent->status and if succeeded - redirect to commerce_payment.checkout.return (StripePaymentElement onReturn)
2. If order is locked (another payment is in the process) output info to the user and disable checkout complete button.
3. Add customer to PaymentIntent::update along with payment_method. Prevents authentication_required, payment_intent_authentication_failure errors and avoids orphaned PaymentMethods.
4. If $intent->amount !== $order_total perform PaymentIntent::update right on the Review Pane. We know this is also done on OrderPaymentIntentSubscriber, but added it just in case because we may sometimes have errors on OrderPaymentIntentSubscriber.