PanelEdit: Include description of what "auto" decimals does

[joshhunt]

What happened:

The behaviour of "auto" decimals for panel options can be a bit confusing as it will round the number based on some logic (which I don't totally understand??). We want to keep this as the default behaviour (as it produces better values for data we see most often in Grafana, like aggregates from Prometheus), but the field should have a description describing this behaviour briefly.

Separately, we should look to include an option or unit/value formatter to just include all decimals #49388

Made this dashboard as an example of auto decimal rounding https://play.grafana.org/d/5Lo_lHm4z/esc-3553-decimal-rounding?orgId=1

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

Environment:

• Grafana version:
• Data source type & version:
• OS Grafana is installed on:
• User OS & Browser:
• Grafana plugins:
• Others:

[joshhunt]

Panel edit options are called "field configs" in the code, and a description should go here https://github.com/grafana/grafana/blob/fa4abdcce16f5f56557c5369800594c2ec27eabf/public/app/core/components/OptionsUI/registry.tsx/#L279-L282