[TIMOB-10351] Android: Timers (setTimeout, setInterval) leak memory.

Timers on Android currently never release the callback function once the timer has finished (fired once or was cancelled). A leak will be created since the callback function and any objects it retains will never get collected.

Timer leak example

function startTimer() {
  // 1 mb buffer
  var buffer = Ti.createBuffer({length: 1024 * 1024});

  setTimeout(function() {
    alert('Buffer: length = ' + buffer.length);
  }, 2000);
}

var win = Ti.UI.createWindow();

var startTimerButton = Ti.UI.createButton({title: 'Start timer'});
startTimerButton.addEventListener('click', startTimer);
win.add(startTimerButton);

win.open();

1. Run the test code and monitor the heap usage with DDMS. 2. Click the "Start timer" button and wait for an alert. 3. Dismiss the alert once it is shown and check the heap usage in DDMS. 4. Repeat steps 2-3 and watch for heap growth. Expected: No long term growth in heap size should happen. It should reach a equilibrium. Actual: The heap grows indefinitely eventually running out of memory.