Added toString implementation for TransactionSimulatorResult (#5957)

Signed-off-by: Shritesh <shritesh.sj@gmail.com>
Co-authored-by: Sally MacFarlane <macfarla.github@gmail.com>

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/transaction/TransactionSimulatorResult.java

@@ -79,4 +79,15 @@ public class TransactionSimulatorResult {
   public int hashCode() {
     return Objects.hash(transaction, result);
   }
+
+  @Override
+  public String toString() {
+    return "TransactionSimulatorResult{"
+        + "transaction="
+        + transaction
+        + ", "
+        + "result="
+        + result
+        + "}";
+  }
 }