fix($sceDelegate): make resourceUrlWhitelist() is identical trustedResourceUrlList()

In commit a206e2675c, `$sceDelegateProvider`'s
`resourceUrlWhitelist()` was deprecated in favor of the new
`trustedResourceUrlList()`. However, although both properties were
assigned the same value, it was possible for an app to break if one of
the properties was overwritten in one part of the app (or a 3rd-party
library) while another part of the app interacts with the other,
non-overwritten property.

This commit fixes it by making `resourceUrlWhitelist()` a getter/setter
that delegates to `trustedResourceUrlList()`, ensuring that the two
properties will remain in sync. This, also, makes it consistent with
other similar deprecated properties, such as `$sceDelegateProvider`'s
`resourceUrlBlacklist()`.

Closes #17090

src/ng/sce.js

@@ -215,7 +215,26 @@ function $SceDelegateProvider() {
     }
     return trustedResourceUrlList;
   };
-  this.resourceUrlWhitelist = this.trustedResourceUrlList;
+
+  /**
+   * @ngdoc method
+   * @name $sceDelegateProvider#resourceUrlWhitelist
+   * @kind function
+   *
+   * @deprecated
+   * sinceVersion="1.8.1"
+   *
+   * This method is deprecated. Use {@link $sceDelegateProvider#trustedResourceUrlList
+   * trustedResourceUrlList} instead.
+   */
+  Object.defineProperty(this, 'resourceUrlWhitelist', {
+    get: function() {
+      return this.trustedResourceUrlList;
+    },
+    set: function(value) {
+      this.trustedResourceUrlList = value;
+    }
+  });
 
   /**
    * @ngdoc method