pkg/cli: add --log-format flag to debug zip for parquet output

[Abhinav1299]

Previously, debug zip collected log files in text format only. For large clusters, node logs can constitute 60-80% of the total debug zip size. While text logs compress well with gzip (~9x compression), the format offers no queryability benefits and the compression ratio is limited by the row-oriented nature of text logs.

This change introduces an optional --log-format flag for the cockroach debug zip command that supports two values: "text" (default, preserving existing behavior) and "parquet". When parquet format is selected, log entries are written using Apache Parquet columnar storage with ZSTD compression. Parquet achieves ~92% compression on raw log data through columnar storage, dictionary encoding on repetitive fields (severity, channel, file paths), and delta encoding on timestamps. The resulting parquet files can be analyzed using SQL-based tools like DuckDB.

The implementation adds a new logParquetWriter that maps logpb.Entry fields to a 15-column parquet schema. The getLogFiles function in zip_per_node.go branches based on the format flag, calling either the existing FormatLegacyEntry for text or the new writeLogEntriesAsParquet for parquet output.

Part of: CRDB-59104
Epic: none
Release note (cli change): Added --log-format flag to cockroach debug zip command. Valid values are "text" (default) and "parquet". The parquet format uses columnar storage with ZSTD compression, reducing raw log size.

[blathers-crl]

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[cockroach-teamcity]

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