Change log for LINUX_DHCP

Date Changes
2023-11-10 Enhancement-
Added a new Grok pattern to parse new type of unparsed logs of format SYSLOG.
2022-09-05 Enhancement-
Migrated the custom parsers into default parser.
2022-08-19 Fix-
- Added a new grok for the logs with timestamp of ISO8601 format.
- Mapped sc_summary to "security_result.summary".
- Mapped chaddr1 to "principal.mac".
2022-08-04 Enhancement
-Parsed logs of type "dhcpd" which were not handled earlier.
-Added check for ciaddr,chaddr.
-Mapped "src_ip" to "principal.ip".
-Mapped "metadata.event_type" to "STATUS_UPDATE" where type includes "RELEASE" and ciaddr is null.
-Mapped "metadata.event_type" to "STATUS_UPDATE" where "metadata.event_type" to "GENERIC_EVENT" and "src_ip" is not null.