feat(filters): add auditd support to linux filter v5.0.0

- Support native auditd collector JSON format (type: auditd)
- Map auditd fields to Standard Event Schema:
  - syscall/category -> action
  - result -> actionResult
  - exe/comm -> origin.process
  - proctitle -> origin.command
  - subj_user -> origin.user
  - cwd -> origin.path
  - exit -> statusCode (cast to int)
- Set default severity 'info' for auditd events
- Preserve numeric IDs in log.* for correlation rules
- Maintain backwards compatibility with journald format

Author: yllada