Inventory Item new fields and ProductVariant deprecations

As of Admin GraphQL API 2024-04, there will be new fields exposed on InventoryItem (and related input types) and some fields on ProductVariant (and related input types) that were marked as deprecated.

For InventoryItem and related input types:

• InventoryItemMeasurement and InventoryItemMeasurementInput were added as new types, with a single field: weight (which is a Weight type).
• measurement was added as a field to InventoryItem.
• harmonizedSystemCode, measurement, and requiresShipping were all added as input fields to InventoryItemInput.

For ProductVariant and related input types:

• fulfillmentServiceEditable, weight, and weightUnit were all marked as deprecated on ProductVariant.
• harmonizedSystemCode, requiresShipping, weight, and weightUnit were all marked as deprecated on ProductVariantInput and ProductVariantBulkInput.

These changes are all in support of removing long-deprecated fields on ProductVariant and removing the duplicated fields between ProductVariant and InventoryItem.