[To rel/0.13] [IOTDB-2669] C++ client optimize the values type in tablet class

[liruizhi19]

C++ client optimize the values type in tablet class.

The old values type is: std::vector<std::vectorstd::string> values;

The new values type is: std::vector<void*> values;

For eliminating two bytes conversion, so the performance is improved. performance test.xlsx