Refactor VelocityTracker_test

Two changes here:
1) Use std::unique_ptr to pass a newed MotionEvent around. This also
fixes a memory leak in computeAndCheckQuadraticEstimate
2) Make pointerCoords and pointerProperties consistent by making them
both arrays

Bug: none
Test: atest -a libinput_tests inputflinger_tests
Change-Id: I4439342c78b1850a9a43bd8c58501f2bc86f266e
Merged-In: I4439342c78b1850a9a43bd8c58501f2bc86f266e