Pass TaskSnapshot object to content suggestion service.

To easier track where do access the HardwareBuffer from a TaskSnapshot
object. And release the reference as soon as possible.

Remove unused members.

Flag: com.android.window.flags.release_snapshot_aggressively
Bug: 238206323
Test: atest TaplOverviewIconTest
Test: atest FlickerTestsNotification
Change-Id: I8e633371153515013ebded52c93fe62d94f8bd30