Fix express checkout methods dependency

[hsingyuc]

Fixes #3828

Changes proposed in this Pull Request:

• Add is_payment_request_enabled flag to show or hide Apple Pay and Google Pay on the checkout page
• Filter express payment types before rendering express checkout buttons

Screen.Recording.2025-02-05.at.11.14.44.AM.mov

Testing instructions

1. With the feature flag off -- this is the default -- verify that Amazon Pay is not available in Stripe settings or in any store page.
2. Turn the feature flag on, by setting the _wcstripe_feature_amazon_pay option to yes.
3. Verify that Amazon Pay is now available in Stripe settings.
4. Go to WC->Settings->Payments->Stripe->Express checkouts section
5. Uncheck Apple Pay / Google Pay, make sure that Link and Amazon Pay are checked
6. Visit the classic checkout page (cart, product, and pay-for-order pages) and see that only the Link and Amazon Pay buttons are rendered
7. Go back to the settings page and uncheck Link and save
8. Visit the classic checkout page (cart, product, and pay-for-order pages) and see only Amazon Pay button is rendered
9. Test other scenarios and make sure there are no regressions.

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• 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)

[diegocurbelo]

It works as expected for the Product page, the Shortcode Cart and the Shortcode Checkout, however on the Blocks Cart and Blocks Checkout pages Google Pay is still visible.

Are you planning on implementing this for the Blocks pages in another PR? If so, I'll approve this one.

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[hsingyuc]

@diegocurbelo, thank you for catching that! Fixed in 7ee6ce7.