The `isScheduler()` util bug is causing observables created by `of()` to be hanged

Bug Report

Current Behavior
The observable created by of() operator is hanged if the param object has the property name schedule with a function value.

Expected behavior
The observable created by of() operator should never hanged if the param object has the property name schedule with a function value.
This bug is quite annoying because objects with the schedule field of function type is not rare.

Reproduction

• REPL or Repo link:
  https://stackblitz.com/edit/rxjs-jw2uu9?file=index.ts

import { of } from 'rxjs';

const value = {
  schedule: function() {}
  //... my other data fields here
};

of(value).subscribe(console.log); // the value is never printed

Environment

• Runtime: node v14.16.1
• RxJS version: 7.3.0

Possible Solution
maybe to have extra/special identity field for the internal Scheduler objects in order to detect them precisely.

Start with the isScheduler() utility and the of() entry point, then reproduce the behavior using the linked StackBlitz example. Done means an observable created with of() emits an object whose schedule property is a function instead of hanging.