Debounce or otherwise improve mapToScreen

[trvrb]

The function mapToScreen updates x,y geometry for the tree. It's expensive. Unfortunately, we need to call it when updating visibilities (via date slider or otherwise) because changing branch thickness means we need to slightly adjust branches to avoid overlap.

Currently, this is a major bottleneck to animation speed. Each animation frame this has to be called. For current flu 3y region I'm getting a 75ms frame in which 20ms is mapToScreen. On these occasions it's not critical that mapToScreen be run every render cycle.

A simple fix should be to add a debounce. This has been called after visibility is changed and other things update. It can be disabled entirely during map animation I suspect. And run after animation paused.