widget: plotter mini-widget

[ES-Alexander]

Problem to solve

Some data is useful to track over time, but only requires general trend / spike information, so high frequency and precision aren't necessary. A plotter widget can capture that, but takes room from the main interface, and is hard to make very small.

Desired approach

A mini-widget equivalent of the current plotter widget with 5-10 data-points, like this example from @Williangalvani:

Ideally there would be options for:

• Line plots
  • like the current standard plotter widget
• Column plots
  • like the image example
• Circular "progress"/pie charts
  • to highlight variables where the state is more important than changes, like for storage usage
• A fixed colour, and also three-point gradient colouring based on a value range
• A label, with horizontal or vertical text
  • or an icon

Similar to the very generic indicator, it would be nice to provide some presets for common variables (e.g. network latency and system RAM and CPU usage as column plots, and disk usage as a circular chart).

I think it is not important to show the actual value or units - if that's important it can be added separately via a very generic indicator.

Additional context

Building off #1525, it would be nice (but not essential) if this could be defined within the existing plotter widget definition.

Mildly related to #85.

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.