Adjust cameraEquals function to use epsilon15

[ggetz]

Changed this value initially in #6115, adjusted it to use epsilon15.

[cesium-concierge]

@ggetz, thanks for the pull request! Maintainers, we have a signed CLA from @ggetz, so you can review this at any time.

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[mramato]

Thanks @ggetz!

For those wondering about this change, because some of the camera values are computed, we can't guarantee they will always be exactly the same. We ran into a few views where this check failed even though the camera hadn't moved. This fixes that (and at 15 decimal places, won't miss any small changes).