Fix grid task dismiss animation when desktop large tile is enabled (1/4)

- Fix bottom grid row size in createTaskDismissAnimation to subtract all large tiles from bottom row count.
This fixes the animation when dismissing a focused and a bottom row task turns into a focused task.

- Fix when snapping to last task, snap to focused task page instead of INVALID_PAGE (-1).
This prevents snapping to a wrong page (DesktopTask page) when last grid task is dismissed.

Bug: 353948136
Bug: 353948182
Flag: com.android.launcher3.enable_large_desktop_windowing_tile
Test: OverviewDesktopTaskImageTest
Change-Id: Ib4b0453eb6b99855615b22fe842ccbe1205c962d