Collect automatic-tax billing address for US bank accounts (MOBILESDK-4667)

[cttsai-stripe]

Summary

Apply the shared automatic-tax billing-address behavior to the separately rendered US bank account form.

This is the special-form companion to the normal LPM integration in #13713. It uses the explicit shared address configuration from #13717 and preserves the behavior-neutral LPM migration in #13723.

Motivation

US bank account bypasses the normal UiDefinitionFactory pipeline, so #13713 deliberately excludes it. Without explicit wiring here, billing-sourced automatic-tax sessions would still omit required address fields on this path.

This PR:

• threads the stable automatic-tax billing requirement into US bank account form arguments;
• uses country-first BillingAddressElement collection with shared per-country tax minimums;
• renders and validates only visible fields as country changes;
• keeps last-text-field and same-as-shipping behavior correct; and
• preserves non-Checkout, disabled-tax, Full-collection, and autocomplete behavior.

JIRA: MOBILESDK-4667

Testing

• Added tests
• Modified tests
• Manually verified

USBankAccountFormViewModelTest covers US, CA, and country-only requirements, dynamic country changes, completion, automatic-tax gating off, and existing Full-address behavior. :paymentsheet:detekt and :paymentsheet:apiCheck passed.

Screenshots

N/A.

Changelog

N/A - Checkout Session is behind @CheckoutSessionPreview; the implementation is internal.