Update app-elements with `useResourceList`

[gciotola]

What I did

Updated from ResourceList to useResourceList in the following points:

• [x] customers > list of customer's orders
• [x] promotions > coupons list page
• [x] sku-lists > manual items
• [x] webhooks > list of event callbacks
• [x] webhooks > list of webhooks

Small improvements

• added skeleton template in webhooks list
• improve delete action on promotions > coupons list page leveraging new removeItem

How to test

Checklist

• [ ] Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests).
• [ ] Make sure to add/update documentation regarding your changes.
• [ ] You are NOT deprecating/removing a feature.

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