Plugin Support

.......... [ZBXNEXT-8330] added default metric support functions for Zabbix agent 2 and plugins

* commit '61ed4a9d924633504d77abe38e7a03aeaa8d18a8':
  ..........[ZBXNEXT-8330] fixed metrics with connection parameters with non-empty hardcoded values
  .......... [ZBXNEXT-8330] fixed defaults and added unit test to eval params
  .......... [ZBXNEXT-8330] added default metric support functions for Zabbix agent 2 and plugins