Change log for FORESCOUT_NAC

Date Changes
2024-04-22 Bug-fix:
- Removed drop condition to parse unparsed logs.
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.