Eliminate the GlanceStackTrace interface, and reuse the Dart's StackTrace interface

[littleGnAl]

The GlanceStackTrace interface is a specialized implementation representing the stack trace for the glance library. By reusing Dart’s StackTrace interface, it simplifies the integration of glance stack traces with other libraries that directly accept a StackTrace object as a parameter, such as Firebase’s recordError API, the user can report the jank stack trace like this:

class JankReportError extends Error {
  @override
  String toString() {
    return 'This only indicates jank, not an actual error.';
  }
}

class MyJankDetectedReporter extends JankDetectedReporter {
  @override
  void report(JankReport info) {
    FirebaseCrashlytics.instance.recordError(JankReportError(), info.stackTrace, fatal: false);
  }
}