FeatureFlag: roll out of 'gitaly_log_command_stats' - logging of rusage stats for shelled out commands

What

Rollout of gitaly_log_command_stats.

Owners

• Team: o11y
• Most appropriate slack channel to reach out to: #sre_observability
• Best individual to reach out to: @igorwwwwwwwwwwwwwwwwwwww

Expectations

What release does this feature occur in first?

13.4 (!2368 (merged))

### What are we expecting to happen?

Additional fields logged.

What might happen if this goes wrong?

Increase in CPU/memory, crashes.

What can we monitor to detect problems with this?

Gitaly service dashboard. Gitaly host dashboard.

Beta groups/projects

None. Percentage based rollout on traffic.

Roll Out Steps

• Read the documentation of feature flags
• Add featureflagstaging to this issue
• Enable on staging
• Test on staging
• Ensure that documentation has been updated
• Announce on the issue an estimated time this will be enabled on GitLab.com
• Add featureflagproduction to this issue
• Enable on GitLab.com by running chatops command in #production
• Cross post chatops slack command to #support_gitlab-com and in your team channel
• Announce on the issue that the flag has been enabled
• Remove feature flag and add changelog entry
• Close this issue