Small QoL improvements for Matcap panels

I love matcaps, but it takes too many clicks and too much time to go through them since the panel immediately closes when you make a selection. Especially if you have a longer list filled with additional matcaps from various other sources besides the default ones, it can quickly become annoying trying to find the right one. I have two small proposals to make this a bit easier:

1. Let the panel stay open until you move your mouse out of bounds so you can immediately try another one if you're not happy with the one you selected. This also makes it consistent with how these panels currently behave with all the other options (you don't have to re-open the Overlays panel after you enable Wireframe, for instance, why should it be different with matcaps?).
2. Add buttons on both sides of the current matcap sphere to go forwards and backwards through all the options so you don't have to open the panel, and you don't have to take your eyes off your model.

Thanks!