Improve UX for equations

### Problem Statement

It's currently not possible (or at least not consistently) to choose whether to also plot intermediate data series on charts vs. just the result of the equation.

### Solution Brainstorm

Implement a common pattern for all visualisation types.


### Product Area

Unknown

No files, tests, or entry points are named. Start by locating the chart visualisation types and the existing equation controls, then compare how intermediate series are currently selected across them. Done means a consistent way to choose intermediate data series or only the equation result for every visualisation type.

Written by the indexing model from the issue text.