Adds "is_variant" filter for Part API (#9077)

* Adds "is_variant" filter for Part API

* Bump API version

src/frontend/src/tables/part/PartTable.tsx

@@ -269,6 +269,12 @@ function partTableFilters(): TableFilter[] {
       description: t`Filter by parts which are templates`,
       type: 'boolean'
     },
+    {
+      name: 'is_variant',
+      label: t`Is Variant`,
+      description: t`Filter by parts which are variants`,
+      type: 'boolean'
+    },
     {
       name: 'is_revision',
       label: t`Is Revision`,