Change TAPL to swipe to stash taskbar (instead of deprecated long press)

This also means Taskbar is transient by default in automated tests,
instead of persistent. Updated some checks accordingly.

Flag: LEGACY ENABLE_TRANSIENT_TASKBAR ENABLED
Test: TaskbarExpandCollapse#hideShowTaskbar; TaplTestsTaskbar;
TaplTestsTransientTaskbar; TaplTestsPersistentTaskbar
Bug: 270395798

Change-Id: Ib6e592a31a55a912a7ea991a421a9c60bca51c80