refactor: PR comments

- rename utils.rs to group_swaps.rs
- extend instead of push in order to avoid calling abi_encode_packed again

src/encoding/evm/strategy_encoder/mod.rs

@@ -1,4 +1,4 @@
+mod group_swaps;
 pub mod strategy_encoder_registry;
 mod strategy_encoders;
 mod strategy_validators;
-mod utils;