Document setting image repositories for job-executor, initcontainer (and distributor)

[christian-kreuzberger-dtx]

From https://keptn.slack.com/archives/CNRCGFU3U/p1658399682503239

We need to document in our Installation docs on how to install and use Job-Executor from a different container registry. This requires setting images for

• job-executor-service itself (--set image.repository, see

  job-executor-service/chart/values.yaml

  Lines 3 to 7 in 16c217d

  	image:
  	repository: docker.io/keptncontrib/job-executor-service
  	pullPolicy: IfNotPresent
  	# Overrides the image tag whose default is the chart appVersion.
  	tag: ""

  ),
• initcontainer (--set jobexecutorserviceinitcontainer.image.repository; see

  job-executor-service/chart/values.yaml

  Lines 9 to 12 in 16c217d

  	jobexecutorserviceinitcontainer:
  	image:
  	repository: docker.io/keptncontrib/job-executor-service-initcontainer # Container Image Name
  	tag: "" # Container Tag

  )
• as well as distributor for as long as we still have it (--set distributor.image.repository; see

  job-executor-service/chart/values.yaml

  Lines 18 to 21 in 16c217d

  	image:
  	repository: docker.io/keptn/distributor # Container Image Name
  	pullPolicy: IfNotPresent # Kubernetes Image Pull Policy
  	tag: "0.16.0" # Container Tag

  ).

Acceptance Criteria

• The aforementioned installation options are documented in docs/INSTALL.md