Control command from the outside of the current run

[mtitov]

• Trigger to create JSON files (registry, tmgr, pmgr dumps)
  • radical-pilot-registry-dump [<session_id>]

Additionally, would propose to consider another command, we didn't discuss it, just thought that it could be part of this ticket as well (also ok to move it to the separate ticket/PR)

• Terminate session gracefully
  • trigger termination command (dump JSONs, close/stop all components)
  • being able to execute either from login node (if client was started from the login node) or compute node (to terminate agent and that will terminate client, if client is started from the login node).