[ECE] On Pay for Order page only pass an order subtotal to express payment method and pass line item data if opted into

[james-allan]

Fixes #3479

Changes proposed in this Pull Request:

This PR brings the pay for order page ECE buttons in line with how line items are handled on the cart and checkout pages.

By default, the Express payment buttons will only display a breakdown by line item if you hook onto the wc_stripe_payment_request_hide_itemization and return false.

For example:

Default	Returning false

Testing instructions

1. Enable ECE via the _wcstripe_feature_ece option in the database.
2. Go to WooCommerce → Orders → Add order
3. Add your current user as the customer
4. Add multiple line items with various quantities (including x1)
5. Click the pay order link.
6. On the Pay for Order page click the Link, Google Pay or Apple Pay button.
7. In the popup, expand the order details.
   • On develop you will see the line item breakdown (with no qty data).
   • On this branch it should say Subtotal with a single total.

develop	This branch
The line item breakdown is shown by default without the qty which is inconsistant

8. Add the following code snippet.

add_filter( 'wc_stripe_payment_request_hide_itemization', '__return_false' );

9. Refresh the Pay for Order page.
10. Click the Link, Google Pay or Apple Pay button.
11. In the popup, expand the order details you should now see the item breakdown with correct qty data.

^{The line item breakdown is now shown including quantities}

---

• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[Mayisha]

This is working correctly and showing the itemized entry depending on the wc_stripe_payment_request_hide_itemization filter.

Default

With wc_stripe_payment_request_hide_itemization filter set to false