New mutations fulfillmentOrderSplit and fulfillmentOrderMerge that enables to split and merge Fulfillment Orders

As of API version 2023-07 partners will be able to split and merge fulfillment orders. Patners can split a single fulfillment order into multiple fulfillment order dividing the line line items across multiple fulfillment orders. Partners can also merge fulfillment orders together into a single fulfillment order

Learn more about fulfillmentOrderSplit [here] (https://shopify.dev/docs/api/admin-graphql/unstable/mutations/fulfillmentOrderSplit) and fulfillmentOrderMerge [here] (https://shopify.dev/docs/api/admin-graphql/unstable/mutations/fulfillmentOrderMerge)