[C++] Address feedback from Todd re var data representation.

It is more-idiomatic to represent variable-length data using `std::string` even when there is no character encoding specified, the the `std::string` API provides useful utilities regardless.

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppDtoGenerator.java

@@ -724,8 +724,6 @@ private void generateVarDataDecodeWith(
  if (token.signal() == Signal.BEGIN_VAR_DATA)
  {
  final String propertyName = token.name();
- final Token varDataToken = Generators.findFirst("varData", tokens, i);
- final String characterEncoding = varDataToken.encoding().characterEncoding();
  final String formattedPropertyName = formatPropertyName(propertyName);
 
  final boolean isOptional = token.version() > 0;
@@ -739,19 +737,8 @@ private void generateVarDataDecodeWith(
  .append(blockIndent).append("const char* ").append(dataVar)
  .append(" = codec.").append(formattedPropertyName).append("();\n");
 
- final String dtoValue;
- final String nullDtoValue;
-
- if (characterEncoding == null)
- {
- dtoValue = "std::vector<std::uint8_t>(" + dataVar + ", " + dataVar + " + " + lengthVar + ")";
- nullDtoValue = "std::vector<std::uint8_t>()";
- }
- else
- {
- dtoValue = "std::string(" + dataVar + ", " + lengthVar + ")";
- nullDtoValue = "\"\"";
- }
+ final String dtoValue = "std::string(" + dataVar + ", " + lengthVar + ")";
+ final String nullDtoValue = "\"\"";
 
  if (isOptional)
  {
@@ -1129,29 +1116,13 @@ private void generateVarDataEncodeWith(
  if (token.signal() == Signal.BEGIN_VAR_DATA)
  {
  final String propertyName = token.name();
- final Token lengthToken = Generators.findFirst("length", tokens, i);
- final String lengthTypeName = cppTypeName(lengthToken.encoding().primitiveType());
- final Token varDataToken = Generators.findFirst("varData", tokens, i);
- final String characterEncoding = varDataToken.encoding().characterEncoding();
  final String formattedPropertyName = formatPropertyName(propertyName);
  final String varName = toLowerFirstChar(propertyName) + "Vector";
 
  sb.append(indent).append("auto& ").append(varName).append(" = dto.")
  .append(formattedPropertyName).append("();\n")
  .append(indent).append("codec.put").append(toUpperFirstChar(propertyName))
- .append("(");
-
- if (null == characterEncoding)
- {
- sb.append("reinterpret_cast<const char*>(").append(varName).append(".data()), ")
- .append("static_cast<").append(lengthTypeName).append(">(").append(varName).append(".size())");
- }
- else
- {
- sb.append(varName);
- }
-
- sb.append(");\n");
+ .append("(").append(varName).append(");\n");
  }
  }
  }
@@ -1629,9 +1600,7 @@ private void generateVarData(
  if (token.signal() == Signal.BEGIN_VAR_DATA)
  {
  final String propertyName = token.name();
- final Token varDataToken = Generators.findFirst("varData", tokens, i);
- final String characterEncoding = varDataToken.encoding().characterEncoding();
- final String dtoType = characterEncoding == null ? "std::vector<std::uint8_t>" : "std::string";
+ final String dtoType = "std::string";
 
  final String fieldName = "m_" + toLowerFirstChar(propertyName);
  final String formattedPropertyName = formatPropertyName(propertyName);