ci.jenkins.io: upgrade datadog plugin from 8.x to 9.x

[dduportal]

Service(s)

ci.jenkins.io

Summary

Same as #4377

As the past attempts to upgrade the datadog plugin (ref. #4080) did corrupt the Jenkins Home, we have to be careful.

Besides, the 9.x version has fixes related to the StackOverFlow errors which created mayhem in the past, as per the plugin author: jenkinsci/datadog-plugin#389 (comment)

We need to:

• Check changelog and user feedbacks
  • https://plugins.jenkins.io/datadog/releases/
• Announce operation
• Take a backup of the data disk (snapshot)
• Perform upgrade and check carefully the results
• Rollback snapshot if any error happens due to datadog

Reproduction steps

No response