"Play" mode repaints gui each frame

[emilk]

Try running examples/python/notebook/cube.ipynb and turn on the performance metrics, and you'll see:

(see top left corner)

When "Play" hits the end it should probably stop, or at least we shouldn't be calling request_repaint unless there are new log events arriving.

[emilk]

The fix should be the same as for #2077

[emilk]

This regression happened in a recent refactor of re_viewer, where the request_repaint was moved

[jleibs]

The fix for this regressed other behavior.
See: #2103

[jleibs]

Fix for the regression: #2106