Fix snapshot starting window stuck if the task never gain focus

The tasksnapshot starting window could stuck on task if the task never
gain focus, this could happen when launch multiple tasks to front, e.g.
split screen, or add snapshot starting window to a pip task.

As using task focus to judge the task snapshot removal may error-prone.
(i.e. unexpected window focus in/lost, non-focusable task window..)

To ensure the tasksnapshot removal works stable, extanding
MAX_DELAY_REMOVAL_TIME_IME_VISIBLE timeout from 450ms to 600ms and also
reference mayImeShowOnLaunchingActivity to know whether IME showing on
this activity.

Bug: 199377815
Bug: 201264769
Bug: 200778734
Test: atest ActivityRecordTests StartingSurfaceDrawerTests
SplashscreenTests
Test: manual launch apps with IME from Recents.
Test: enter pip, power on/off, verify starting window is removed.
Test: manual enter split screen, verify starting window is removed.

Change-Id: I81b048a655124923a5f19e7f236511502bbf4c91
(cherry picked from commit a4f760be)