Cone traces with irregular grids do not scale cone correctly

[etpinard]

See https://codepen.io/etpinard/pen/gKMJyZ that has the default sizemode and sizeref and compare with https://codepen.io/etpinard/pen/eKzawB?editors=0010 that has sizeref: 10. Cone should always be visible using the default sizeref so something is off.

I believe this is (another) side-effect of our dataScale hack (more on that in: #2646) where sizeref: 1 should correspond to two cones of max norm at the minimal adjacent position just touching each other. But by the time gl-cone3d computes the max length the x/y/z positions and u/v/w vectors are scaled meaning that we should also scale sizeref before passing it to gl-cone3d. Doing this might be tricky as x/y/z and u/v/w are vectors and sizeref is a scalar, but hopefully there's a way to do so in plotly.js.

If so, fixing this should also fix #2700

[etpinard]

by irregular I mean grids that generate unequal x-axis, y-axis, z-axis ranges.

[etpinard]

Closed in #2715 (for now at least)