feat(sync): MerkleStage (#994)

Co-authored-by: lambdaclass-user <github@lambdaclass.com>
Co-authored-by: Francisco Krause Arnim <fkrausear@gmail.com>

crates/primitives/src/proofs.rs

@@ -20,7 +20,7 @@ pub const EMPTY_ROOT: H256 =
 
 /// A [Hasher] that calculates a keccak256 hash of the given data.
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
-pub(crate) struct KeccakHasher;
+pub struct KeccakHasher;
 
 impl Hasher for KeccakHasher {
     type Out = H256;