This commit implements the design task #78398
- Box region
- Set Custom UV Region (Ctrl-B).
- Disabled with Custom Region checkbox in the menu or (Ctrl-Alt-B).
- Box Select (Pinned) changed to (Alt-B).
- When the Custom Region enum is chosen the islands are packed
into the bounding box of the drawn region.
Ref !140020
a9a54c88b9