AML: Support concurrent launches

Now the transition info doesn't associate to windowing mode.
A consecutive launch is identified by checking if the caller
is existing in an active transition. Since the global states
and timestamps are moved to TransitionInfo, different
transitions can be tracked individually.

Bug: 123355661
Test: atest ActivityMetricsLaunchObserverTests
            ActivityMetricsLoggerTests

Change-Id: I07aeedd0d525b4bee94809e487aa84cdcb300cf3