Add dismiss to ApplePayContext

[yuki-stripe]

Summary

See https://stripe.slack.com/archives/C0353FPANQ0/p1736808910348399

Motivation

https://jira.corp.stripe.com/browse/MOBILESDK-2987
#3558

Testing

Added unit test, does not actually test we call cancel under the hood though.

Manually tested calling the cancel API after I receive the payment method:

Simulator.Screen.Recording.-.snapshot.tester.iPhone.12.mini.16.4.-.2025-01-13.at.15.59.20.mp4

Changelog

See CHANGELOG

[github-actions]

⚠️ Public API changes detected:

StripeApplePay

- public func dismiss(completion: StripeApplePay.STPVoidBlock? = nil)

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• Does this require a breaking version change?
• Do these changes require API review?

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