Setup renovate.json to monitor Istio Operators 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: You should be able to test this with renovate running manually on your machine. Automation is not required. To verify, set the branch to your development branch and purposely set the image versions/SHAs to an older value. Verify the dependency dashboard is created as an issue. Verify a branch and merge request with the updated versions/SHAs is created. Update the versions/SHAs to the latest values (either merge the MR with branch deletion or update with a commit, close the MR, and delete the branch). Re-run renovate and verify the dependency dashboard issue automatically closes since everything is up-to-date.