Update Viewer on preUpdate instead of clock tick

[lilleyse]

This changes the viewer to be updated on preUpdate rather than clock tick from this idea in #7204.

This allows entity changes to be reflected in the pick pass.

I'm a little hesitant about making a core change like this but it seems mostly safe as clock.tick() and scene.render() are called right after another in CesiumWidget.

this branch vs. master

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
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Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

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[hpinkos]

This seems okay with me. I'll let @mramato make the call on this though

[mramato]

Looks like you have some test failures.

I've actually wanted to explore making this change ever since we added the pre/post render events. I'm honestly not that worried about it (because as you said, the tick/preRender always get called back to back in our own internal render loop).

That being said, we should still hammer on this before merging, so I'll take a look at it now.

[mramato]

Can we name this _onPreUpdate just so it's more obvious.

[lilleyse]

Renamed the function and fixed the tests (had the commit locally but forgot to push - it shows up above the comments).

[mramato]

Thanks @lilleyse. The build failed for seemingly unrelated reasons that looks like they might be related to external urls.