Screenshot Policy updates

Corrections and improvements:

   The information returned is now more carefully identified:

   * CaptureParameters now have a distinct field 'contentTask'
     from the 'owner'. This information is used for followup
     screenshot actions which operate on a single app window,
     such as scroll capture search and assist content query.

   * This field usually (but not always) represents the
     focused task. This task can frequently belong to a user
     other than the owner of the screenshot.

   Several additional cases are now correctly handled:

   * If there is a Private profile app in a Picture-In-Picture
     window, the screenshot is now directed to the private
     profile.

   * If a work profile app is in desktop mode, with a maximized
     window it will be treated the same as full screen, saved
     with a task snapshot and assigned to the work profile
     user.

Bug: 365597999
Flag: com.android.systemui.screenshot_policy_split_and_desktop_mode
Test: atest ScreenshotPolicyTest
Change-Id: Ife74e54e54c2fca526a761eb061d5d0c323b7ef4