Zabbix

.......PS. [ZBX-23200] fixed parsing NULL values, multiline strings and quoted strings in SNMP walk output

Merge in ZBX/zabbix from feature/ZBX-23200-6.4 to release/6.4

* commit 'fbb6b051332668bab27a31e2420c61eee796a03b':
  .......PS. [ZBX-23200] fixed value initialization for NULL values in SNMP walk output
  .......... [ZBX-23200] added cmocka test cases to snmp walk to value preprocessing
  .......... [ZBX-23200] added cmocka test cases for snmp walk to value preprocessing
  .......... [ZBX-23200] added cmocka test cases for unquoted multiline tests
  .......... [ZBX-23200] added changelog file
  .......PS. [ZBX-23200] fixed parsing escaped backslashes and double quotation marks in SNMP walk output
  .......PS. [ZBX-23200] added support of unquoted strings in SNMP walk output
  .......PS. [ZBX-23200] added support of NULL values in SNMP walk output

(cherry picked from commit 04d4ed2cdda04f5a17abe26d1f0219d3697dde09)