Add top_level to span debug output

[ajgajg1134]

What Does This Do

Add top_level to debug span output when the span is marked top_level

Motivation

We already mark measured spans, but those aren't the only spans that have stats calculated. The missing field here would have made a recent debugging of a customer issue easier

Additional Notes

This is my first time contributing to this repo so I might have missed some steps or something here :P. I lack permissions to set labels myself too so I can't fully follow the below checklist

Contributor Checklist

• Format the title according the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any useful labels
• Don't use close, fix or any linking keywords when referencing an issue.
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, move, or deletion
• Update the public documentation in case of new configuration flag or behavior

Jira ticket: [PROJ-IDENT]