Improve types of testing utilities and fix some types in unit test code (#26122)

* Improve type of DeepPartial and make mergeObjects handle Sets/Maps properly

* Fix linting

* Remove undefined fields from menu_cloud_trial.test

* Prevent importing the wrong version of DeepPartial

webapp/platform/types/src/utilities.ts

@@ -16,6 +16,9 @@ export type IDMappedObjects<E extends {id: string}> = RelationOneToOne<E, E>;
 export type DeepPartial<T> = {
     // For each field of T, make it optional and...
     [K in keyof T]?:
+        // If that field is a Set or a Map, don't go further
+        T[K] extends Set<any> ? T[K] :
+        T[K] extends Map<any, any> ? T[K] :
         // If that field is an object, make it a deep partial object
         T[K] extends object ? DeepPartial<T[K]> :
         // Else if that field is an optional object, make that a deep partial object