drop runExtension support for customer account ui extension

[brianshen1990]

Background

Part of step 4 ( have to do it in ui-extension side as well ) of this ticket https://github.com/Shopify/core-issues/issues/63160

Please also review customer account web side PR: https://github.com/Shopify/customer-account-web/pull/3701

1. customer account repo: support render customer-account.order.action.menu-item.render if it is within return extension https://github.com/Shopify/customer-account-web/pull/3679
2. return repo: add an customer-account.order.action.menu-item.render target extension and remove the CustomerAccount::Returns::Initiate target extension ( after step 1 is deployed ) https://github.com/Shopify/buyer-returns/pull/372
3. customer account repo: remove requestReturn logic https://github.com/Shopify/customer-account-web/pull/3699
4. customer account repo: remove the legacy CustomerAccount::Returns::Initiate
   • customer account web side: https://github.com/Shopify/customer-account-web/pull/3701
   • ui extension side drop runExtension support for customer account ui extension #1658
5. customer account repo and return repo: once soft auth customer account api is supported, move the whether to render request return logic to return app
6. drop the support for CustomerAccount::Returns::Initiate in core https://github.com/Shopify/shopify/blob/f646c61cdfe69b47ed1c9a82eff8d29eb866c7e0/components/apps/app/services/apps/models/ui_extension/schema/groups/customer_account_ui.rb

Solution

(Describe your solution, why this approach was chosen, and what the alternatives/impacts may be)

🎩

See tophat of this ticket https://github.com/Shopify/customer-account-web/pull/3701

Checklist

• I have 🎩'd these changes
• I have updated relevant documentation

[robin-drexler]

So beautiful! It's been a long time coming. ❤️

[lihaokx]

LGTM