evals: eval crate overhaul, simplification and performance improvements

evaluations/src/slice/build.rs

@@ -0,0 +1,19 @@
+use sha2::{Digest, Sha256};
+
+#[derive(Debug)]
+pub(super) struct BuildParams {
+    pub include_impossible: bool,
+    pub base_seed: u64,
+    pub rng_seed: u64,
+}
+
+#[allow(clippy::indexing_slicing)]
+pub(super) fn mix_seed(dataset_id: &str, seed: u64) -> u64 {
+    let mut hasher = Sha256::new();
+    hasher.update(dataset_id.as_bytes());
+    hasher.update(seed.to_le_bytes());
+    let digest = hasher.finalize();
+    let mut bytes = [0u8; 8];
+    bytes.copy_from_slice(&digest[..8]);
+    u64::from_le_bytes(bytes)
+}