Support fog in planar reflections

[johnrossporter]

Please describe the desired feature/behaviour.

In the built-in pipeline, fog is currently not visible in the planar reflection capture. This can result in a reflection that does not match what is being reflected very well. Ideally, we would the fog to show up in the capture.

This is a general issue with Unity and most implementations of planar reflections, and appears in other projects. See the following threads for some discussion.

https://forum.unity.com/threads/fog-on-reflections-in-water.503190/ https://answers.unity.com/questions/681123/water-4-advanced-fog-missing-from-reflections.html