Trackpad: View3D Zoom and Dolly improvements and fixes.
Some time ago, there was an initial code here that only supports `MOUSEZOOM`,
then `MOUSEPAN` support was added but this code was not adapted for it.
For "Dolly", `MOUSEPAN` support was completely missed.
At this point: `16ca65e4a91b`, direction for all (Trackpad, Mouse, Scroll Wheel)
was consistent, Zooming In - move mouse/fingers towards screen.
Later, Apple changed the default trackpad setting to "Natural", and now the trackpad zoom is reversed.
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With this patch the trackpad respects the Zoom Axis option,
and the zoom direction is always consistent with the mouse and gizmo.
Note that the "Trackpad Natural" preference must be set correctly, see D8550.