ci.jenkins.io: upgrade datadog plugin from 7.x to 8.x

[dduportal]

Service(s)

ci.jenkins.io

Summary

Same as #4236

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

We need to:

• Check changelog and user feedbacks (as it's been a few weeks since last release)
  • https://plugins.jenkins.io/datadog/releases/#version_8.0.0
• 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