3.0 Custom palettes

Custom palettes act differently. Most of it is not an improvement.

1. All custom palettes default to able to be edited. In version 2.x, custom palettes based upon advanced defaulted to being able to be edited, while those created based on basic palettes were not able to be edited by default.

2. After closing and reopening MuseScore, all custom palettes get reset to editable rather than the use selected state. See #167171: Make custom palettes based upon advanced workspace default to not enable editing.

3. You cannot reorder items in a palette by dragging them (like you could in version 2), you must delete items and reenter them in the palette in the new order.

4. You cannot accidentally reorder items in the palette by dragging them a little (a byproduct of 2&3). This is actually good but fixing 2&3 above would keep this true.