Migrate fog volumes to required components (#15568)

# Objective

Another part of the migration to required components: fog volumes!

## Solution

Deprecate `FogVolumeBundle` and make `FogVolume` require `Transform` and
`Visibility`, as per the [chosen
proposal](https://hackmd.io/@bevy/required_components/%2FcO7JPSAQR5G0J_j5wNwtOQ).

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## Migration Guide

Replace all insertions of `FogVolumeBundle` with the `Visibility`
component. The other components required by it will now be inserted
automatically.