Add NestedDraggable.shouldConsumeNestedPreScroll()

This CL adds a shouldConsumeNestedPreScroll() callback to
NestedDraggable so that it can consume scroll events before nested
scrollable.

This CL also renames shouldConsumedNestedScroll() to
shouldConsumedNestedPostScroll(), to make it more explicit when it is
called.

Bug: 397989775
Test: atest NestedDraggableTest
Flag: EXEMPT new unused API
Change-Id: I63b7f3295e22aa0c75f1648d6c2ee409a763bcbd