Add renovate support for Grafana Iron Bank images

Requirements:

• renovate.json used as the configuration file
• Creates auto-closing dependency dashboard to avoid noise in issue creation
• Monitors main branch only
• Auto creates a branch and merge request with the following changes:
  • References to image version are updated to latest version
  • References to SHAs are updated to latest version
  • Branch is NOT automatically merged

Testing:

• Can be tested using automated pipeline/job or manually with renovate on your machine
• Verify dependency dashboard is created as an issue when version/SHA is out-of-date
• Verify no issue is created when version/SHA is up-to-date
• Tips:
  • You must re-title issues created if you want renovate to create another one. Closing it is not enough.
  • You can point renovate.json to your development branch and set the versions/SHAs to obsolete versions for testing.
  • Understand the versioning scheme you are using to make sure it works for the releases. Docker will work for Iron Bank.