Change log for FORESCOUT_NAC

Date	Changes
2024-02-05	Enhancement: - Mapped "eventtype" to "additional.fields".
2024-01-29	Bug-Fix: - Added new Grok patterns to parse CEF logs. - Added condition to avoid conversion failure for "principal.port". - Mapped "username" to "principal.user.userid". - Mapped "action" to "security_result.action_details". - Mapped "resource" to "principal.resource.name". - Mapped "command" to "principal.process.command_line". - Mapped "version" to "metadata.product_version". - Added Grok patterns to parse the missing field values in description. - Mapped "source_ip" to "principal.asset.ip". - Mapped "target_ip" to "target.asset.ip". - Mapped "computer_name" to "target.asset.hostname". - Mapped "destination" to "target.asset.hostname". - Mapped "Target" to "target.asset.hostname". - Mapped "Hostname" to "principal.asset.hostname". - Mapped "Source" to "principal.asset.hostname". - Mapped "middle_ip" to "intermediary.asset.ip". - Mapped "iporhost" to "intermediary.asset.hostname". - Mapped "Host" to "principal.asset.hostname".
2023-12-21	Bug-Fix: - Added new Grok patterns for unparsed SYSLOG logs. - Mapped "CPU usage", "Available memory", "Used memory", "Available swap", "Used swap", "Application status", "Connected Clients", "EM connection status", "Assigned hosts", "Engine status" and "Installed plugins" to "additional.fields". - Added condition to check if message contains "CEF:" to parse "CEF" logs.
2023-05-31	Enhancement: - Enhanced parser to reduce "GENERIC_EVENT" and set the "metadata.event_type" to a more appropriate value.
2022-10-07	Enhancement: - Enhanced the parser to support CEF format logs.