Makes it possible to swipe over panel header to batch open/collapse all
panels the mouse draged over. Normal panels and sub-panels support this
too.
Two changes were needed:
- Support "drag toggle" feature for `UI_BTYPE_BUT_TOGGLE` - all toggle
buttons should/can support this.
- Allow querying the pushed state from the button used for the
collapsing. Multiple ways to do this, in this case simply using the
pushed state query callback seemed simplest.
Pull Request: https://projects.blender.org/blender/blender/pulls/114560
ecbb77c558