Sample in a bounded HSV color space to improve color contrast against object selection, section and sketcher planes.

I'm a heavy user of "object random color" when working. The current object color randomization can be pretty awful, selecting ultra-bright colors that conflict with the sketcher workplane, or impossible to distinguish dark hues.

This changes the random color to select mostly dull but still distinguishable colors that always have good contrast in all view modes (uniform, flat or shadow) and most non-solid/UI elements (sketches, pre/selections, and so on). This is similar in what several commercial CADs already do, although I noticed at least some cycle through a fixed unsaturated palette (onshape, *cough*).

Before:

After:

Loading some random model with several parts, this is how the current random object colors tend to fare while trying to pick the worst result in both with flat shading:

With the PR:

This is still implemented as a single-shot randomization without neighboring analysis (that is, we don't try to maximize contrast with close neighbors). Doing that would drastically improve the contrast against parts without having to change the colormap, although if you have "object random color" bound to a hotkey this is already not bad and orders of magnitudes better than the current status.