Cisco Secure Email Gateway | Use CEF processor instead of GROK for Consolidated Event logs

Currently, `cisco_secure_email_gateway` uses GROK to parse consolidated event logs. Since these consolidated logs are in Common Event Format (CEF), we could use `cef` processor instead to improve parsing performance.

Reference - [Consolidated Event Logs](https://www.cisco.com/c/en/us/td/docs/security/ces/user_guide/esa_user_guide_14-0-2/b_ESA_Admin_Guide_ces_14-0-2/b_ESA_Admin_Guide_12_1_chapter_0100111.html#:~:text=with%20AsyncOS%20API-,Consolidated%20Event%20Logs,-The%20Consolidated%20Event)