Add new metadata fields to json output

Add new metadata fields for experimental measurements to the onionperf json output.

Trac:
Parent Ticket: #33323 (moved)

added component::metrics/onionperf metrics-team-roadmap-2020 owner::metrics-team parent::33323 points::0.5 priority::medium severity::normal sponsor::59-must status::new type::enhancement labels

Trac:
Points: N/A to 0.5

Trac:
Parent: #33322 (moved) to #33323 (moved)

Trac:
Keywords: N/A deleted, metrics-team-roadmap-2020Q1 added

Trac:
Keywords: metrics-team-roadmap-2020Q1 deleted, metrics-team-roadmap-2020 added
Sponsor: N/A to Sponsor59

Moving to Sponsor59-must, because we should really do these in order to call Sponsor59 done.

Trac:
Sponsor: Sponsor59 to Sponsor59-must

changed time estimate to 4h

mentioned in issue #33323 (moved)