Menu slider UI: hover to get a longer slider

Right now, we have menu settings that are sort of sliders, with a circular visual.

In sculpt mode: blend amount, looseness amount, hole, (spraypaint) opacity.

In paint mode: fade, opacity, scatter.

In sound mode: octave spread.

That UI is quite hard to use with any precision. So when it's not limited to just a few notches (eg. octave spread), it's hard to really dial it in to have the exact value we want. This is particularly problematic when changing blend amount; for a large shape a tiny change can make a huge difference in result.

If while hovering over such a setting it would expand downward (similar to the way individual thermos expand horizontally), we would have a lot more room to drag the value around and so have more fine-tuning available to us. It shouldn't have to overlap other menu items, or impact anything else; it simply makes that specific UI element of the menu a lot easier to use.