Update Tapl tests for enable_grid_only_overview

- Add "task" as id for TaskView, and use it instead of "snapshot" when creating OverviewTask, so that for split tasks are caputred as a whole in getCurrentTask and getTasks
- Fix getCurrentTask() to correctly get the top-right tasks in grid only overview. It'll first get the widest task, and then top, and then rightmost task
- Fix scrollLeftByDistance() to correctly account for leftGestureMargin to make sure it scroll by distance provided
- Fix scrollCurrentTaskOffScreen() to actually scroll the task off screen
- Fix createAndLaunchASplitPair() to use Task menu instead of Overview actions for grid only overview
- Skip testOverviewActions() in grid only overview, where Overview actions isn't available
- Fix testOverivewForTablet to expect the correct task in grid only overview; also disabled part of a test due to an animation bug in Overview
- Fix dismissBySwipingUp() to swipe from bottom of task, which is required to effectively dismiss top row tasks
- Also fixed OverviewTask to correctly get objects in FallbackOverview

Bug: 283246928
Test: presubmit
Flag: None
Change-Id: I5dd39b1779ea02738556f921169dbe38aa4cba8c