fix(core): use addCustomEqualityTester instead of overriding toEqual (#22983)

This propagates other custom equality testers added by users. Additionally, if
an Angular project is using jasmine 2.6+, it will allow Jasmine's custom object
differ to print out pretty test error messages.

fixes #22939

PR Close #22983

packages/types.d.ts

@@ -25,3 +25,12 @@ declare namespace jasmine {
     toHaveProperties(obj: any): boolean;
   }
 }
+
+/**
+*Jasmine matching utilities. These are added in the a more recent version of
+*the Jasmine typedefs than what we are using:
+*https://github.com/DefinitelyTyped/DefinitelyTyped/pull/20771
+*/
+declare namespace jasmine {
+  const matchersUtil: MatchersUtil;
+}