Change log for FORTINET_FORTIMAIL

Date Changes
2025-02-25 Enhancement:
- Mapped "type" and "subtype" to "metadata.product_event_type".
- Mapped "to" to "network.email.to".
2023-09-06 Enhancement:
- Added a Grok pattern to extract the data and parse failing KV logs.
2023-05-23 - New parser.