Issues with state navigation at high zoom level

When trying to navigate between states at high zoom levels, using the left & right arrow keys, the selection doesn't skip correctly:

- In the timeline-chart example app, the selection skips between the beginning and end of the absolute range.

- In the theia-trace-extension example app, it seems the selection skips to the next state and then it's only possible to skip between the start and end of that state, until zooming out a little. Notice also the disappearance of states when zooming in (related to #62?).