Disable dialog animation sync on low-RAM devices

In DialogLaunchAnimator, disable animation sync if device is low-RAM.
This is a mitigation to workaround a bug in animations sync which
currently causes the UI to freeze for 4s when opening a dialog on
certain devices.

Also, rename isForTesting to forceDisableSynchronization for clarity

Test: Tap "internet", "power", or "select-user" buttons in QS
Bug: 217621394
Bug: 216391326
Change-Id: I33117466b5002671ee086aedade56737b19c8edb