Bring the packed archive tooling to public builds: the `packed-io`
clickhouse-disks subcommand and the standalone `clickhouse-packed-io`
program, which list, extract and create ClickHouse packed-format
archives (`data.packed`). The implementation (`PackedFilesOperations`,
`CommandPackedIO`, `programs/packed-io`) only depends on the already
public `PackedFilesReader`/`PackedFilesWriter`, so un-gate it from
`#if CLICKHOUSE_CLOUD`.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
