Add a background system task to periodically copy remote statistics in evergreen.yml

For remotely managed hosts, which do not have an Evergreen agent (powercycle task), the post phase copies system and process statistics. In the case of a failure to reach this host these statistics are lost. We can periodically copy them (every 30 seconds), so the information is not completely lost, by doing it in a background system task, "copy ec2 statistics".