Allow multiple agent labels

[MarkEWaite]

Allow multiple agent labels

Workaround for:

• [RPU] builds stuck in trusted.ci.jenkins.io helpdesk#4122

Run with Java 21 no matter which agent

Testing done

Confirmed that the command correctly uses the desired Java version no matter which Java version is in my PATH. Checked with Java 11, Java 17, and Java 21 on my Red Hat Linux 8 with the bash shell. Also tested in Alpine container image.

Reviewer checklist

Preview Give feedback

1. Check that the $pluginId Developers team has Admin permissions while granting the access.
2. In the case of plugin adoption, ensure that the Jenkins Jira default assignee is either removed or changed to the new maintainer.
3. If security contacts are changed (this includes add/remove), ping the security officer (currently @Wadeck) in this pull request. If an email contact is changed, wait for approval from the security officer.

There are IRC Bot commands for it.

[dduportal]

Ah ah we did the same thing at the same time :D (see #3958)

I let you decide which one to merge