Zabbix

...G...PS. [ZBX-24017] added support of null for nodata value in Agent JSON protocol

Merge in ZBX/zabbix from feature/ZBX-24017-6.5 to master

* commit '03d0db1173246f2eb4f4039cc2fa5de654e79815':
  .......... [ZBX-24017] added changelog
  .......... [ZBX-24017] rephrased task timeout error
  ...G...... [ZBX-24017] fixed nodata messages in test and zabbix_get
  ...G...... [ZBX-24017] fixed crash when getting null vlaue from cgo
  ...G...... [ZBX-24017] reverted capacity changes
  ...G...PS. [ZBX-24017] refactored
  ...G...... [ZBX-24017] aligned json format in agent1
  ...G...... [ZBX-24017] fixed value field always present in error response
  ...G...... [ZBX-24017] added nil checks
  ...G...... [ZBX-24017] simplified code in manager.go:PerformTask()
  ...G...... [ZBX-24017] fixed logging in handleCheck
  ...G...... [ZBX-24017] simplified
  ...G...... [ZBX-24017] added zabbix_get changes
  ...G...... [ZBX-24017] added sending of null instead of string nil in agent JSON protocol
  ...G...... [ZBX-24017] added overriding of max plugin capacity
  .......PS. [ZBX-24017] fixed null value history caching