Rewrite and reorganize metrics #962
Description
The metrics page has a lot of info. Some things we could do to make the flow better:
- Split the reference off to its own page (like with options)
- Add grpc and websockets metrics (Update built-in metrics #471)
- Possibly make a gatsby component to place these references in two places: in their respective API doc, and together on a single page (Investigate ways to template and reuse content #797)
- Link reference to or from results output, since metrics are just results ouput (or move metrics to that section)
- Make new how to page for custom metrics:
- Move examples for custom metric types there
- Do a bit more to help readers understand these metrics
- What info does a gauge convey that a trend cannot?