perf(l1): change encode_to_vec().len() -> length(), avoiding encoding to calc rlp length (#5374)

**Motivation**

Followup on  #5350 since its already a big pr.

Changed:
- Replaced encode_to_vec().len() calls with length()
- Added more tests

---------

Co-authored-by: Tomás Grüner <47506558+MegaRedHand@users.noreply.github.com>

Author: edg-l

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Perf
 
+### 2025-11-28
+
+- Change some calls from `encode_to_vec().len()` to `.length()` when wanting to get the rlp encoded length [#5374](https://github.com/lambdaclass/ethrex/pull/5374)
+
 ### 2025-11-20
 
 - Improve rlp encoding by avoiding extra loops and remove unneeded array vec, also adding a alloc-less length method the default trait impl [#5350](https://github.com/lambdaclass/ethrex/pull/5350)

crates/blockchain/blockchain.rs

@@ -1754,7 +1754,7 @@ pub fn validate_block(
         .map_err(InvalidBlockError::from)?;
 
     if chain_config.is_fork_activated(Osaka, block.header.timestamp) {
-        let block_rlp_size = block.encode_to_vec().len();
+        let block_rlp_size = block.length();
         if block_rlp_size > MAX_RLP_BLOCK_SIZE as usize {
             return Err(error::ChainError::InvalidBlock(
                 InvalidBlockError::MaximumRlpSizeExceeded(

crates/blockchain/payload.rs

@@ -243,7 +243,7 @@ impl PayloadBuildContext {
         let vm_db = StoreVmDatabase::new(storage.clone(), parent_header);
         let vm = new_evm(blockchain_type, vm_db)?;
 
-        let payload_size = payload.encode_to_vec().len() as u64;
+        let payload_size = payload.length() as u64;
         Ok(PayloadBuildContext {
             remaining_gas: payload.header.gas_limit,
             receipts: vec![],

crates/common/types/block.rs

@@ -900,7 +900,9 @@ mod test {
             requests_hash: Some(*EMPTY_KECCACK_HASH),
             ..Default::default()
         };
-        assert!(validate_block_header(&block, &parent_block, ELASTICITY_MULTIPLIER).is_ok())
+        assert!(validate_block_header(&block, &parent_block, ELASTICITY_MULTIPLIER).is_ok());
+        assert_eq!(parent_block.encode_to_vec().len(), parent_block.length());
+        assert_eq!(block.encode_to_vec().len(), block.length());
     }
 
     #[test]

crates/common/types/transaction.rs

@@ -3445,10 +3445,12 @@ mod tests {
 
         let encoded = PrivilegedL2Transaction::encode_to_vec(&privileged_l2);
         println!("encoded length: {}", encoded.len());
+        assert_eq!(encoded.len(), privileged_l2.length());
 
         let deserialized_tx = PrivilegedL2Transaction::decode(&encoded)?;
 
         assert_eq!(deserialized_tx, privileged_l2);
+
         Ok(())
     }
 

crates/l2/monitor/widget/blocks.rs

@@ -113,7 +113,7 @@ impl BlocksTable {
                     block.header.coinbase,
                     block.header.gas_used,
                     block.header.blob_gas_used,
-                    block.encode_to_vec().len(),
+                    block.length(),
                 )
             })
             .collect::<Vec<_>>();

crates/l2/sequencer/block_producer/payload_builder.rs

@@ -99,7 +99,7 @@ pub async fn fill_transactions(
     let VMType::L2(fee_config) = context.vm.vm_type else {
         return Err(BlockProducerError::Custom("invalid VM type".to_string()));
     };
-    let mut acc_encoded_size = context.payload.encode_to_vec().len();
+    let mut acc_encoded_size = context.payload.length();
     let fee_config_len = fee_config.to_vec().len();
 
     debug!("Fetching transactions from mempool");
@@ -152,7 +152,7 @@ pub async fn fill_transactions(
 
         // Check if we have enough blob space to add this transaction
         let tx: Transaction = head_tx.clone().into();
-        let tx_size = tx.encode_to_vec().len();
+        let tx_size = tx.length();
         if acc_encoded_size + fee_config_len + tx_size > SAFE_BYTES_PER_BLOB {
             debug!("No more blob space to run transactions");
             break;

crates/networking/rpc/types/block.rs

@@ -72,9 +72,7 @@ impl RpcBlock {
         hash: H256,
         full_transactions: bool,
     ) -> Result<RpcBlock, RpcErr> {
-        let size = Block::new(header.clone(), body.clone())
-            .encode_to_vec()
-            .len();
+        let size = Block::new(header.clone(), body.clone()).length();
         let body_wrapper = if full_transactions {
             BlockBodyWrapper::Full(FullBlockBody::from_body(body, header.number, hash)?)
         } else {

crates/vm/levm/src/hooks/l2_hook.rs

@@ -692,7 +692,7 @@ fn calculate_l1_fee_gas(
         return Ok(0);
     };
 
-    let tx_size = vm.tx.encode_to_vec().len();
+    let tx_size = vm.tx.length();
 
     let l1_fee = calculate_l1_fee(fee_config, tx_size)?;
     let mut l1_fee_gas = l1_fee