Handle both mouse wheel and trackpad

[TedDriggs]

The current code ignores magnitude differences in deltaY, resulting in an experience that is either too fast on trackpad or too slow with a mousewheel.

This change allows those to differ within a clamped range, so that one zoomSpeed value works well for both input devices.

Fixes #1882

[jeffrey-e]

Looking forward to this improvement!

[TedDriggs]

@Thomaash could you take a look at this PR? Having a fix for this would let us remove a very clunky workaround in our app where we have to give the user a setting to tell us which input device they're using.