Zabbix

...G...... [ZBXNEXT-6651] added new item agent.variant for Agent and Agent2

Merge in ZBX/zabbix from feature/ZBXNEXT-6651-5.0 to release/5.0

* commit '1259d980dcb19d634beaa2d6ecc3e4e1237f564e':
  ...G...... [ZBXNEXT-6651] fixed PR warning
  ...G...... [ZBXNEXT-6651] changed items order
  .D........ [ZBXNEXT-6651] added ChangeLog
  ...G...... [ZBXNEXT-6651] added new item agent.variant for Agent
  ..F....... [ZBXNEXT-6651,ZBXNEXT-7012] added new item key "agent.variant" to the helper for selecting item keys