devx: Attach metadata to Buildkite steps to identify step owners

Created by: marekweb

Why: We want to be able to add additional information to help diagnose issues with build steps.

For each step in Buildkite, the name of a step "owner" (e.g. a team) would be attached so that we can quickly triage who should be notified, or who should be responsible, for build issues.

The metadata will be included in build traces for each job.