Change log for ZSCALER_TUNNEL

Date Changes
2025-06-04 - Adding support for the legacy log format in the ZSCALER_TUNNEL parser.
2025-04-30 - Promoted ZSCALER_TUNNEL Premium parser to default. You can see full details in the parser configuration page - https://cloud.google.com/chronicle/docs/ingestion/default-parsers/ingest-zscaler-logs