Generate new constants for 2D View Coordinates

[jleibs]

What

View Coordinates aren't limited to 3D. Generate constants for 2D ViewCoordinates using the existing type and leaving the 3rd dimension Unused.

We might also consider setting the third coordinate for just force right-handed spaces, or always force Z-forward to make sense in the context of our depth offset concept.

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Deployed docs

Commit	Link
fa35387	https://landing-3fnpxalzi-rerun.vercel.app/docs