[Benchmark datasets] Add a sorted ClickBench benchmark dataset

[gabotechs]

Part of #629.

Add a deterministic ClickBench dataset variant whose Parquet data is globally sorted by an explicitly documented key (or key sequence). This should make physical data ordering a controlled benchmark dimension, separate from the existing ClickBench layout.

Scope:

• Add the Rust preparation code and gen-clickbench-sorted.sh generation entry point.
• Write the dataset to a distinct slash-style dataset path, such as testdata/clickbench-sorted/<variant>.

For a more detailed explanation of how to wire this up, see #629