feat(l2): introduce FlatTrie as a zkVM performant MPT

crates/blockchain/blockchain.rs

@@ -34,6 +34,7 @@ use ethrex_rlp::encode::RLPEncode;
 use ethrex_storage::{
     AccountUpdatesList, Store, UpdateBatch, error::StoreError, hash_address, hash_key,
 };
+use ethrex_trie::flattrie::FlatTrie;
 use ethrex_trie::node::{BranchNode, ExtensionNode};
 use ethrex_trie::{Nibbles, Node, NodeRef, Trie};
 use ethrex_vm::backends::levm::db::DatabaseLogger;
@@ -988,7 +989,7 @@ impl Blockchain {
         } else {
             Trie::new_temp()
         };
-        let mut storage_trie_roots = BTreeMap::new();
+        let mut storage_tries = BTreeMap::new();
         for key in &keys {
             if key.len() != 20 {
                 continue; // not an address
@@ -1011,16 +1012,18 @@ impl Blockchain {
                     "execution witness does not contain non-empty storage trie".to_string(),
                 ));
             };
-            storage_trie_roots.insert(address, (*node).clone());
+            storage_tries.insert(address, FlatTrie::from(&(*node)));
         }
 
+        let state_trie = state_trie_root.map(|n| FlatTrie::from(&n));
+
         Ok(ExecutionWitness {
             codes,
             block_headers_bytes,
             first_block_number: first_block_header.number,
             chain_config: self.storage.get_chain_config(),
-            state_trie_root,
-            storage_trie_roots,
+            state_trie,
+            storage_tries,
             keys,
         })
     }