message: hammer: improved performance in dump for deeply nested values
diff: @@ -6789,9 +6789,9 @@ class basic_json
  // variable to hold indentation for recursive calls
  const auto new_indent = current_indent + indent_step;
  - if (indent_string.size() < new_indent)
  + if (JSON_UNLIKELY(indent_string.size() < new_indent))
  {
  - indent_string.resize(new_indent, ' ');
  + indent_string.resize(indent_string.size() * 2, ' ');
  }
  // first n-1 elements
  