Apache Airflow Google provider: Path traversal via GCS object names → local/SFTP filesystem (GCSToSFTPOperator + GCSTimeSpanFileTransformOperator)

Apache Airflow's Google provider operators `GCSToSFTPOperator` and `GCSTimeSpanFileTransformOperator` joined GCS object names returned by the bucket listing API directly to a destination filesystem path without normalisation or containment check. A user with write access to the source GCS bucket (typically a different trust principal than the DAG author — partner uploads, ingest-only service accounts, public-data buckets) could create an object whose name contains `..` segments and cause the DAG run to write the downloaded blob outside the configured destination (the SFTP `destination_path` for `GCSToSFTPOperator`; the worker-local temp directory for `GCSTimeSpanFileTransformOperator`), enabling overwrite of arbitrary files on the SFTP server or the worker host. Affects deployments that ingest from buckets writable by less-trusted principals. Users are advised to upgrade to `apache-airflow-providers-google` 22.2.1 or later.