Logs the activated session duration for magnification. (2/2)

Uses the atom MagnificationFollowTypingFocusActivatedSessionReported in
westworld to log the activated session duration for the window magnifier
which its following typing focus is enabled.

The duration is accumulated by the time when the window magnifier and
the ime are all on. If one of them is off, we would pause the
accumulated timer. If a user moves the window magnifier to disables
this function, we would stop the accumulated timer and log the duration.

Bug: 216733714
Test: m statsd_testdrive & statsd_testdrive 453
      atest WindowMagnificationManagerTest
Change-Id: I994fc2a3ada8a90fde8b3a0b4f1cc8d7ec21638a
Merged-In: I994fc2a3ada8a90fde8b3a0b4f1cc8d7ec21638a