Zabbix

........S. [ZBX-23690] optimized maintenance calculations for large number of hosts and maintenances

Merge in ZBX/zabbix from feature/ZBX-23690-6.4 to release/6.4

* commit '2a412b699d3668735732a2c42e98a538f1422ce8':
  .D........ [ZBX-23690] added changelog entry
  ........S. [ZBX-23690] optimized maintenance calculations for large number of hosts x maintenances