fix(dashboard,admin-shared): Fixes to inventory page (#8941)

**What**
- Adds qty column to reservations table.
- Adds missing injections zones
- Fixes layout on long description field.

Resolves CC-121

packages/admin-next/admin-shared/src/extensions/widgets/constants.ts

@@ -189,6 +189,15 @@ const RETURN_REASON_INJECTION_ZONES = [
   "return_reason.list.after",
 ] as const
 
+const INVENTORY_ITEM_INJECTION_ZONES = [
+  "inventory_item.details.before",
+  "inventory_item.details.after",
+  "inventory_item.details.side.before",
+  "inventory_item.details.side.after",
+  "inventory_item.list.before",
+  "inventory_item.list.after",
+] as const
+
 /**
  * All valid injection zones in the admin panel. An injection zone is a specific place
  * in the admin panel where a plugin can inject custom widgets.
@@ -220,4 +229,5 @@ export const INJECTION_ZONES = [
   ...PRODUCT_TYPE_INJECTION_ZONES,
   ...PRODUCT_TAG_INJECTION_ZONES,
   ...RETURN_REASON_INJECTION_ZONES,
+  ...INVENTORY_ITEM_INJECTION_ZONES,
 ] as const