Update drr equality (#1469)

* Update drr equality

* null === null

* Array length compare

* isFunction(next.eq)

* Just JSON.stringify on compare

* Add distinctUntilChanged in  rpc-core

* prev/next -> a/b

packages/api-derive/src/util/drr.ts

@@ -22,7 +22,9 @@ export const drr = (): DrrResult => <T> (source$: Observable<T>): Observable<T>
 
       throw error;
     }),
-    distinctUntilChanged(),
+    distinctUntilChanged((a: any, b: any): boolean =>
+      JSON.stringify({ value: a }) === JSON.stringify({ value: b })
+    ),
     publishReplay(1),
     refCount()
   );