[Fix] isLabelSyncedWithName should be nullable (#9028)

isLabelSyncedWithName should be nullable for fieldMetadata, as it is for
objectMetadata.

+ Adding missing validation on label and name sync in
fieldMetadataService for creation and update
+ adding metadata tests

packages/twenty-front/src/modules/object-metadata/types/FieldMetadataItem.ts

@@ -39,5 +39,5 @@ export type FieldMetadataItem = Omit<
   settings?: {
     displayAsRelativeDate?: boolean;
   };
-  isLabelSyncedWithName?: boolean;
+  isLabelSyncedWithName?: boolean | null;
 };