Print deprecation warning when using -jnlpUrl

[basil]

Upgrade to the latest release of Remoting, which prints this warning on the client side, and also add a similar warning on the server side as well to maximize the chances that the warning is actually seen by an administrator.

Testing done

Connected with -jnlpUrl and verified that the warning was printed on both the server and client side. Connected with -url and -name and verified that the warning was no longer printed on either the server or client side.

Proposed changelog entries

• The -jnlpUrl ${JENKINS_URL}/computer/${AGENT_NAME}/jenkins-agent.jnlp argument to the agent JAR has been deprecated; use -url ${JENKINS_URL} and -name ${AGENT_NAME} instead, potentially also passing in -webSocket, -tunnel, and/or work directory options as needed.

Proposed upgrade guidelines

• The -jnlpUrl ${JENKINS_URL}/computer/${AGENT_NAME}/jenkins-agent.jnlp argument to the agent JAR has been deprecated; use -url ${JENKINS_URL} and -name ${AGENT_NAME} instead, potentially also passing in -webSocket, -tunnel, and/or work directory options as needed. Official Docker images already use the new calling convention.

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@mention

Before the changes are marked as ready-for-merge:

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[timja]

Nice!

[timja]

/label ready-for-merge

---

This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

Thanks!