docs+fix: add h5bench benchmark results and repair libhdf5-compare feature

Add h5bench-equivalent Criterion benchmark results to BENCHMARKS.md
(sequential read/write, chunked read/write, metadata throughput).

Fix libhdf5-compare feature for HDF5 1.14.x:
- Switch to hdf5-metno 0.12 (aliased as 'hdf5') in clawhdf5-bench
- Fix h5bench_meta.rs: AttributeBuilderEmpty::create takes &str not &String;
  shape=[1] dataset uses write(&[val]) not write_scalar
- Fix h5bench_read.rs: libhdf5-compare variant now writes its own reference
  file via hdf5-metno instead of dumping clawhdf5 bytes (avoids float
  datatype message incompatibility)

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

crates/clawhdf5-bench/benches/h5bench_meta.rs

@@ -49,7 +49,7 @@ fn bench_metadata_attrs_write(c: &mut Criterion) {
                 ds.write(&[1.0f64, 2.0, 3.0]).unwrap();
                 for i in 0..k {
                     ds.new_attr::<i64>()
-                        .create(&format!("attr_{i:04}"))
+                        .create(format!("attr_{i:04}").as_str())
                         .unwrap()
                         .write_scalar(&(i as i64))
                         .unwrap();
@@ -137,7 +137,7 @@ fn bench_metadata_groups_create(c: &mut Criterion) {
                         .shape([1])
                         .create("x")
                         .unwrap()
-                        .write_scalar(&0.0f64)
+                        .write(&[0.0f64])
                         .unwrap();
                 }
             });