Populate RunConfiguration Artifacts from RunCompletionEvent

[jmendesky]

Set Artifacts in RunConfiguration State as follows:

kind: RunConfiguration
spec:
  run:
    ...
  triggers:
    ...
  artifacts:
  - name: an-artifact
     ...
status:
  latestRuns:
    succeeded:
      ...
      artifacts:
      - name: an-artifact
        location: gs://some/where

Depends on #246 and #249