frontend: map: make context menu radial

Current behaviour

The context menu is linear, and option ordering is not aligned with expected relative usage, so there's a fair amount of unnecessary movement required to select a desired option, and it needs to be vertically precise.

Expected or desired behaviour

Make the menu radial (like in Houdini?), to minimise movement required to get to each option,

and support gestures (like in Fusion360?), so power users are less distracted by UI elements they don't need to see:

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.