PointerLocationView: Do not scale touch and tool axes when drawing

The touch and tool axes in MotionEvent use display pixels as their unit,
so it is incorrect to scale them when drawing.

Instead, to make the orientation arrow more visible in
PointerLocationView, make the minimum size for the arrow 24dp, instead
of the old minimum of 20 pixels.

Bug: 285045978
Test: manual
Change-Id: I0d30c7bf0ad8cd833434229a9f6fc03c80ada6fd