s2: send traces to Cloud Traces

Created by: bobheadxi

It appears we are exceedingly unlikely to be allowed to export data to Honeycomb: https://sourcegraph.slack.com/archives/C02MWRMAFR8/p1658333474452259

reference: https://docs.google.com/document/d/1GiOPJjuYrUahrZnENSLUCsujo2MCu2v_gw23SKNzE6E/edit#bookmark=id.82bg1iwuw5sc

Honeycomb might still be valuable as a development tool - in environments we control, engineers can use it to understand general trends - but if we're talking about improving observability of Cloud instances, the outlook on Honeycomb looks grim. We probably want to start trialing Cloud Tracing in s2 just in case

Links:

• https://pkg.go.dev/github.com/open-telemetry/opentelemetry-collector-contrib/exporter/googlecloudexporter#section-readme
• https://github.com/sourcegraph/infrastructure/pull/3683