Replace more obvious private API usages in view CTS tests

Removes some unnecessary overrides, imports, and method calls. Also
removes the entirety of OnComputeInternalInsersListener tests from
ViewTreeObserver since that class is framework-private.

Inverts some assertions for dispatch tests since a real ViewGroup
dispatches to children. The previous tests were basically no-op since
setParent() was just setting a class variable and not setting up a
real view hierarchy.

Moves scrollbar tests to use XML rather than code since we deprecated,
removed, and no-op'ed the behavior of initializeScrollbars().

Bug: 13281485
Change-Id: Ie48b807be5f0d15645acfb86dd5db4469125cbff
7 files changed