Refactor and streamline initialization of rendering

[philippotto]

There are a lot of separate components which interact with each other during initialization of the core dataset/tracing view. I think there is some potential to improve the process. I'd hope that we can:

• Remove ugly delays/polling mechanism or other setTimeout hacks (e.g., setTimeout usage in camera_controller.js and waitForCondition in input_catcher.js)
• Be more robust towards subtle side-effects of layout changes (e.g., the new flexlayout mechanism had side-effects on how a dataset is rendered by default; see Fix initial zoom/rotation + nightly #5453)
• As a consequence, improve performance during loading

[philippotto]

the first point is about to be fixed by #8996. the other two points are not really actionable, which is why I'm closing this issue now.