UI Chart - Change config UI for multiple "Series" definitions

### Description

Currently, we follow the Dashboard 1.0 model of:

- Single chart "type"
- single y-axis control/definition

This limits us in doing composite charts (as requested [here](#460)).

As an alternative configuration, we could instead have an interface similar to the dropdown/form UIs, whereby you can add series to the chart, with _each_ series having a chart type, y-property, min/max, etc.

Would also open the possibility of #296/#1070 too

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate