Change log for ZSCALER_FIREWALL

Date Changes
2023-09-12 Enhancement:
- Handled unparsed JSON format logs.
2023-03-28 Enhancement - Added some null checks and on_error statements to handle parsing errors.
- Added/Modified Grok patterns to parse the logs with CEF format.
- Handled the cases when "port", "received_bytes" or "ip" were not in their correct form.
2022-04-29 - Migrated to default parser.
- Converted from SDM to UDM.
2022-04-29 - Migrated to default parser.
- Converted from SDM to UDM.
2022-04-14 - Added new data element for secure result
- Modified mapping for target application, network duration