Adds three Criterion benchmark suites mirroring the h5bench HPC I/O
benchmark workloads in pure Rust — no C libhdf5 required for the default
path, with an optional `libhdf5-compare` feature for side-by-side numbers.
- benches/h5bench_write.rs: write_1d_contiguous, write_2d_chunked,
write_f64_batch, write_multi_dataset, write_with_attrs
- benches/h5bench_read.rs: read_sequential, read_f64_sequential,
read_chunked_2d, read_from_disk, read_hyperslab
- benches/h5bench_meta.rs: metadata_attrs_write, metadata_attrs_read,
metadata_groups_create, metadata_groups_traverse, metadata_string_attrs
All benchmarks pass `cargo bench --bench <name> -- --test` and clippy
reports zero warnings. Run with `cargo bench -p clawhdf5-bench`.
Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
