Implement Payment Settings for WeChat Pay

[danielmx-dev]

Description

In #10012 we explored the required work to implement WeChat Pay as a new payment method. This issue focuses on the required changes to enable/disable the Gateway for this new Payment Method via the WooPayments settings screen.

Acceptance criteria

• WeChat Pay can be enabled/disabled for eligible Stripe accounts.
• WeChat Pay is not visible for non-eligible Stripe accounts.

Designs

• TBD.
• Confirm the contents of the payment method description with product/design.

Testing instructions

1. Onboard with a Stripe account from any of the supported countries.
2. WeChat Pay should be available for selection in the WooPayments settings.
3. Enable WeChat Pay
4. Save the settings and refresh, the setting should be persisted.

Other countries:

1. Use a Stripe account from any non-supported country.
2. Go to the WooPayments Settings.
3. WeChat Pay should not be visible.

Dev notes

• Use the Proof of Concept branch as a guide https://github.com/Automattic/woocommerce-payments/compare/poc/wechat-pay?expand=1
  • There are a few things that need to be changed, like the supported countries, or a custom get_countries implementation, so review each piece of code one by one.
• The server fees and capabilities may be required in order to properly display the new Payment Method, mock them if necessary.