Fix forever repaint of big scenes

[emilk]

What

• Closes Endless ui refresh #5018

When first loading a scene, before the user interacts, we want to center the eye-camera on the scene, so each frame we call "interpolate to the default eye". This should be fine, because we have an early-out if we're already at target. However, the interpolation code had a rounding error meaning we reached very close to our goal, but not quite there. In particular, in arkit_scenes it would lead to a forever repaint, since the eye-camera would never reach its target, and so thus would require more animation.

This manifested in arkit_scenes now due to another bug (#5070) causing enormous point clouds, making the rounding errors larger than usual.

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