title	issue
Cleanup for nested LineItems in order of admin	NEXT-14314

Core

Changed parameter type of setChildren in \Shopware\Core\Checkout\Order\Aggregate\OrderLineItem\OrderLineItemEntity from ?OrderLineItemCollection to OrderLineItemCollection
Added parentAssociation and childrenAssociation fields in platform/src/Core/Checkout/Order/Aggregate/OrderLineItem/OrderLineItemDefinition.php

Administration

Removed snippets to be replaced with global.default namespace:
- sw-order.detail.buttonEdit
- sw-order.detail.buttonSave