CI Runner Structured Log Cleanup

Changes that we should make to the CI runners structured logs

• Add unit suffixes to appropriate fields
• Switch from nanosecond based job durations to seconds
• Job completion should be in a different field to job success or failure error message
• Runner version number
• Nice-to-have: context metadata (plan, namespace, etc)
• Nice-to-have (and super helpful): git strategy, repository and SHA details for the job (example: https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/359#note_342291790)

cc @tmaczukin @steveazz