Pass view state through to visualizer systems

[Wumpf]

What

.. and some cleanup on the way

This is an important piece that allows us to move arbitrary heuristics to visualizer implemented fallbacks.
(Fixes main build failure caused by a merge order issue - view systems started using the ViewContext struct before they had access to the view state)

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
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  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
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