Move reverb silder to advanced settings

[ann0see]

What is the current behaviour and why should it be changed?

Currently, the reverb slider takes up a lot of space in the main mixer board. It is assumed that this could be mistaken as general volume slider. In order to simplify the UI, the reverb slider should go to advanced settings instead.

In future - if we support plugins, the reverb feature could be removed and replaced by custom reverb plugins.

Describe possible approaches

Move the slider to advanced settings.

Has this feature been discussed and generally agreed?

See: https://github.com/orgs/jamulussoftware/discussions/3341#discussioncomment-10576183
#2361 (reply in thread)

[ann0see]

This is a UI change and will probably stir confusion for people who are using the reverb slider. They might think that the feature was removed.
Therefore, we must document this and make clear that this makes the UI simpler.