feat: Make executors_file_path optional and use a default value if None

--- don't change below this line ---
ENG-4088 Took 4 minutes

Took 59 seconds

src/encoding/strategy_encoder.rs

@@ -23,7 +23,7 @@ pub trait StrategyEncoder {
 pub trait StrategyEncoderRegistry {
     fn new(
         chain: Chain,
-        executors_file_path: &str,
+        executors_file_path: Option<&str>,
         signer_pk: Option<String>,
     ) -> Result<Self, EncodingError>
     where