Embedded update pt 3

[yuki-stripe]

Summary

Previous PR: #4150
Makes EmbeddedPaymentElement view a view that contains embedded view so we can swap to the updated embedded view with an animation.

Makes EmbeddedPaymentElement restore previous customer in payment method list selection (1) on update, call didUpdateHeight and didUpdatePaymentOption if necessary.

Still to come:

• Restore previous customer input in form (2) + E2E tests (e.g. load PI -> fill out card form -> update to SI -> expect form to be preserved but w/o checkbox)
• Make confirm handle in-flight and failed update calls.
• (Bonus) Cancel network calls etc. from previous update to reduce battery/network usage. Can apply this to FC.update as well.

Motivation

https://jira.corp.stripe.com/browse/MOBILESDK-2583

Testing

See test

Changelog

Not user facing

[emerge-tools]

📸 Snapshot Test

No snapshots generated

Name	Version	Added	Removed	Modified	Unchanged	Errored	Approval
StripePaymentSheetSize com.stripe.StripePaymentSheetSize	1.0 (1)	0	0	0	0	0	N/A
StripePaymentsUISize com.stripe.StripePaymentsUISize	1.0 (1)	0	0	0	0	0	N/A
StripePaymentsSize com.stripe.StripePaymentsSize	1.0 (1)	0	0	0	0	0	N/A
StripeApplePaySize com.stripe.StripeApplePaySize	1.0 (1)	0	0	0	0	0	N/A
StripeFinancialConnectionsSize com.stripe.StripeFinancialConnectionsSize	1.0 (1)	0	0	0	0	0	N/A
StripeSize com.stripe.StripeSize	1.0 (1)	0	0	0	0	0	N/A

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[github-actions]

🚨 New dead code detected in this PR:

EmbeddedPaymentMethodsView.swift:9 warning: Imported module 'StripeCore' is unused

Please remove the dead code before merging.

If this is intentional, you can bypass this check by adding the label skip dead code check to this PR.

ℹ️ If this comment appears to be left in error, double check that the flagged code is actually used and/or make sure your branch is up-to-date with master.