Prevent x-axis window movement during the initial swipe up to show transient taskbar

- If gesture starts and isLikelyToStartANewTask=true, we do not clamp
- If gesture starts and isLikelyToStartANewTask=false AND transient taskbar is not
  already showing, we clamp the scrolling

Bug: 258851206
Test: swipe up to show taskbar, no x-axis movement
      swipe left/right still works as expected

Change-Id: Iac194df63e03b4a28b49008983c88c165847aa31