Change log for ZSCALER_DNS

Date Changes
2026-01-09 - Updated the field mapping for the Zscaler DNS parser.Please refer to the parser documentation page for information regarding the updated UDM mappings - https://docs.cloud.google.com/chronicle/docs/ingestion/default-parsers/zscaler-dns#udm_mapping_delta
2025-11-28 - about.file.full_path: Newly mapped `pcapid` raw log field with `about.file.full_path` UDM field.
2025-05-14 - Backward compatibility code behaved erratically because two fields were getting merged within a single filter. Modified the code to handle this scenario.
2025-04-30 - Promoted ZSCALER_DNS 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