Fix no cross-profile thumbnail animation

As the task of the launching activity requests attaching cross-profile
thumbnail animation but in Transication#onTransitionReady didn't be
promoted into change list, so it ends up no-op since attaching thumbnail
for cross-task requires the animating target is the task.

Fix the issue by
1) Add {FLAG_CROSS_PROFILE_OWNER_THUMBNAIL,
   FLAG_CROSS_PROFILE_WORK_THUMBNAIL} in TransitionInfo.Change for shell
   to know which thumbnail icon should load, according to the userId of
   launching activity.
2) Remove isTask and add 1)'s change flag check in
   attachCrossProfileThumbnailAnimation to make the thumbnail animation
   can be played and attached on the activity-level.

Fix: 239798040
Test: as issue steps
 1) Use Gmail app
 2) Tap the account icon
 3) Select "Switch to personal profile" (or "Switch to work profile")
 4) Expect the dimmed background thumbnail icon with
    task opening transition are animated in parallel
Change-Id: I90eecf4e8ba104c7234a39d1b2638295820d2ac7