Ability to detach an agent from a running process

When monitoring an application via a standalone agent as follows:

`java -javaagent:PATH_TO_APM_AGENT.jar -Delastic.apm.service_name=NEW_NAME -Delastic.apm.server_url=http://HOSTNAME:8200 -jar PATH_TO_APPLICATION_JAR.jar`

it will be beneficial to be able to detach the agent without stopping the application itself.

Use case examples: - Update the agent to a later version. - Agent errors and needs restarting - No further need for monitoring.