docs: Refinery Config copyediting (#734)

## Which problem is this PR solving?

This PR hopes to make the generated `config.yaml` file and associated
documentation the best that it can be.

## Short description of the changes

- [x] Standardize on capitalization for Refinery, Redis, Stress Level
- [x] Add codeblock formatting for fields
- [x] Check on TODOs found (refer to tagged PR comments)
- [x] Clarify existing wording
- [x] Use OpenTelemetry (OTel) consistently throughout config file
without being obnoxious
- [x] Consider Groups descriptions
- [x] Word Wrap descriptions
- [x] Reduce duplicate field summary vs. field descriptions.

---------

Signed-off-by: Mary Jinglewski <maryjinglewski@honeycomb.io>
Co-authored-by: Kent Quirk <kentquirk@honeycomb.io>