Migrate the createBinaryFunction to generate kotlin code properly

Signed-off-by: angrezichatterbox <gouthammohanraj@gmail.com>

Author: angrezichatterbox

codegen/src/main/java/org/web3j/codegen/SolidityFunctionWrapper.java

@@ -416,16 +416,15 @@ PropertySpec createBinaryDefinition(String binary) {
         }
 
         String[] argsArray = binary.split("(?<=\\G.{65534})");
-        StringBuilder stringBuilderString = new StringBuilder().append("new StringBuilder()");
+        StringBuilder stringBuilderString = new StringBuilder().append("StringBuilder()");
         for (String s : argsArray) {
             stringBuilderString.append(".append(\"");
             stringBuilderString.append(
                     s.replaceAll("\\$", "\\$\\$")); // escape $ which bytecode may contain
             stringBuilderString.append("\")");
         }
         stringBuilderString.append(".toString()");
-        return PropertySpec.builder( BINARY, String.class)
-                .addModifiers(KModifier.PUBLIC, KModifier.FINAL, KModifier.FINAL)
+        return PropertySpec.builder( BINARY, ClassName.bestGuess("kotlin.String"))
                 .initializer(CodeBlock.of(stringBuilderString.toString()))
                 .build();
     }