Tweak ColorPinWidget and ColorPicker

[brusherru]

A list of little tweaks:

1. Replace Saturation/Lightness box inside ColorPicker with the triangle, like on the picture below (Affinity Designer)
2. Add the "Revert" button and preview for the initial color inside ColorPicker
3. Render pin widgets in accordance with deduced types on generic pins. So when deduced pin gets #FF00AA bound value it should be replaced with the ColorPinWidget and should provide a ColorPicker. But should be replaced on deducing another type (not when the input is empty). It's an unimplemented part of issue #1945.
4. Show squares with the bound color over the color pins and inside tweak-color and linked watch nodes on the patch board.

[evgenykochetkov]

Also, the little hue selector ring seems to be slightly off-center. Here it's closer to the inner edge: And here it's closer to the outer edge: