RenderContext usage cleanup

[Wumpf]

What

Some cleanup related to recent interior mutability changes: In a lot of places we can now pass just the RenderContext instead of several arguments, making a lot of code less complex. Also, "shared renderer data" is no longer needed either and is flattened out into the RenderContext.

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• I have read and agree to Contributor Guide and the Code of Conduct
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[emilk]

much nicer