title: Flink combination of windowByTime and triggerByCount
body: <pre><code>source.keyBy(0)
      .window(TumblingEventTimeWindows.of(Time.seconds(5)))
      .trigger(PurgingTrigger.of(CountTrigger.of[TimeWindow](2)))
      .process(new TestFun())
  </code></pre>
  <p>Explanation:</p>
  <p>Let's say I have 3 events[E1, E2, E3], which should be trigger by count, and also it should trigger by time.
  I'm using countTrigger to trigger only 2 events(E1 &amp; E2) but the remaining E3 event is not triggering.</p>
  <p><strong>Expected: E3 Event should trigger after the 5 seconds but actually it's triggering only E1 and E2 events</strong></p>