DOC-11726 metrics metadata (#768)

* metrics WIP

* metrics wip

* DOC-11726 update metrics_metadata

After CBG-3637

* DOC-11726: sort keys

Using `jq . --sort-keys`
This will be done on source .json once
https://issues.couchbase.com/browse/CBD-5711
is complete.

* DOC-11726: Metrics Metadata

Correct default for SGW

Author: osfameron