It is a follow-up to JENKINS-48761. Currently Jenkins Core does not specify a minimal-supported version, so users do not even got warnings when they use old Remoting versions without using a Version Column plugin (CC batmat)

I propose to enhance the behavior:

• Define a minimal supported version within the core
• Where to return the data?
  • Make the version available via Jenkins API
  • The minimal supported version should be returned in TcpAgentListener's headers so that Agent can process it on its side
  • Nice2Have: The minimal supported version should returned in the Jenkins WAR Manifest
• Diagnostics:
  • Warning in agent connection log when the version older than the Minimal one is connected. The connection whould not be aborted, user should just know he runs in YOLO mode
  • Warning in the log on the Remoting side (separate ticket - TODO)
  • Nice2Have: Warning on the agent main page
  • Nice2Have: Administrative monitor OR support in Version Column Plugin
  • Nice2Have: Warning in the Support Core plugin