[Filebeat] Add Zeek (formerly Bro) Module

[andrewkroh]

Add a new Filebeat module for ingesting logs from the Zeek Network Security Monitor (formerly Bro).

Filebeat module checklist

• Supported Zeek versions are documented
• Supported operating systems are documented (if applicable)
• Integration tests exist
• Automated checks that all fields are documented
• Documentation for module and required Bro configuration
• Fields follow ECS and naming conventions
• Dashboards exists
• Kibana Home Tutorial
• Test log files exist for the grok patterns
• Generated output for at least 1 log file exists

[elasticmachine]

Pinging @elastic/secops

[andrewkroh]

@alakahakai For the last remaining bullet there is a guide at https://www.elastic.co/guide/en/kibana/current/add-data-guide.html. This adds content to the Kibana home screen's "Add Data" section. You'll see that there is a page for Suricata there too.

[alakahakai]

Added Kibana home tutorial for zeek module - Kibana pull elastic/kibana#31774