Add Prow

[emanuelb]

Details:

• Ci name: Prow
• Website: https://github.com/kubernetes/test-infra/tree/c341b223083a7e5766be99620eba58cc3c8142f1/prow#readme https://docs.prow.k8s.io/docs/overview/
• Default env variables: https://docs.prow.k8s.io/docs/legacy-snapshot/prow/jobs/#job-environment-variables https://github.com/kubernetes/test-infra/blob/c341b223083a7e5766be99620eba58cc3c8142f1/prow/jobs.md#job-environment-variables

looks like PROW_JOB_ID env var can be used to identify Prow.

[sibiraj-s]

Added in v4.0.0