Make it easier to position 3D eye-camera center

[emilk]

What

With this PR, we show the orbit center when using WSAD (and when focusing on an entity).
This makes it much easier to position the orbit center exactly where you want it.

I also removed the scroll-to-move "feature"

• Closes Zooming in changes orbital camera origin #4402

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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