replace hashbrown with std::hashmap

[aneubeck]

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[Copilot]

Pull request overview

This PR updates the hash-sorted-map crate’s benchmark harness and accompanying documentation to compare against std::collections::HashMap (with explicit hashers) rather than benchmarking hashbrown directly, and removes the direct hashbrown dependency from the benchmark crate.

Changes:

• Switch Criterion benchmarks from hashbrown::HashMap/ahash::AHashMap to std::collections::HashMap configured with specific BuildHasher implementations.
• Update README/optimization writeups to report results and comparisons using the new std::collections::HashMap baselines.
• Remove hashbrown from crates/hash-sorted-map/benchmarks dependencies.

Show a summary per file

File	Description
crates/hash-sorted-map/README.md	Updates benchmark comparison labels and adds an explanatory note about std::collections::HashMap/hashbrown.
crates/hash-sorted-map/OPTIMIZATIONS.md	Updates benchmark tables/baselines and clarifies relationship to std::collections::HashMap.
crates/hash-sorted-map/benchmarks/performance.rs	Replaces benchmarked map implementations with std::collections::HashMap variants using explicit hashers.
crates/hash-sorted-map/benchmarks/Cargo.toml	Drops the hashbrown dependency from the benchmark crate.

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• Files reviewed: 4/4 changed files
• Comments generated: 2