[3/n] Reuse default center position for new window if free

If the last focused window is in the center and overlap with new window
exceeds minimum touch target, reuse the center position for the new
window and don't cascade.

Flag: com.android.window.flags.enable_cascading_windows
Test: atest DesktopTasksControllerTest
Bug: 280496681
Change-Id: Id593ae23ec5b0806f71461e3393c1dea16ba6345