dev/dn: include environment, deploy in all events

Created by: bobheadxi

While building a dashboard for https://github.com/sourcegraph/sourcegraph/issues/32153#issuecomment-1094820837 I realized I cant build a chart for per-service deployments because I don't have the environment in child spans of the root deploy trace. This change standardizes on a set of metadata to better help identify all spans.

Test plan

unit tests