fix(block-theme): migrate newspack-theme checkout fixes

[chickenn00dle]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Closes https://linear.app/a8c/issue/NPPD-1188/modal-checkout-testing-and-fixes

This PR moves over some of the styles and fixes from newspack-theme so they also apply to block theme.

How to test the changes in this Pull Request:

• Checkout the fix/modal-checkout-for-block-theme branch for the following repos: newspack-theme, newspack-blocks, and newspack-plugin
• Activate the newspack block theme
• Smoke test modal checkout in various scenarios including:
  • Checkout Button
  • Donate Block
  • One payment gateway
  • Multiple payment gateways
  • Various fields set in Audience > Configuration > Checkout & Payment
  • Anything else you can think of!
• Activate the newspack theme
• Repeat smoke tests
• Finally smoke test standard Woo checkout

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[Copilot]

Pull request overview

Migrates modal checkout UI fixes from newspack-theme into the plugin so they also apply when using the Newspack block theme (especially around WooCommerce checkout/payment UI).

Changes:

• Add WooCommerce checkout hook to render a “Payment info” heading above the payment form.
• Extend Newspack UI WooCommerce overrides with payment-method layout/styling and select2 sizing fixes.
• Adjust Newspack UI table styling to use border-collapse: collapse.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
src/newspack-ui/scss/elements/woocommerce/_overrides.scss	Adds checkout/payment-method and select2 overrides intended to improve modal checkout styling.
src/newspack-ui/scss/elements/_tables.scss	Collapses table borders for more consistent table rendering in UI.
includes/plugins/woocommerce/class-woocommerce-connection.php	Loads the new checkout feature class as part of WooCommerce integration init.
includes/plugins/woocommerce/class-woocommerce-checkout.php	New WooCommerce checkout feature: inserts a payment heading via WooCommerce hook.

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[laurelfulford]

Looks good @chickenn00dle! Just needs a couple CSS tweaks and it should be good to go!

[chickenn00dle]

Thanks @laurelfulford! I applied your suggestions. This should be good for another round of review as well.