fix variable length warning using std::vector

[ijnek]

Resolves: ROBOTIS-GIT/DynamixelSDK#553

Gets rid of the following warning:

Starting >>> dynamixel_workbench_toolbox
--- stderr: dynamixel_workbench_toolbox                              
/home/ijnek/tmp_workspaces/dynamixel_control_ws/src/dynamixel-workbench/dynamixel_workbench_toolbox/src/dynamixel_workbench_toolbox/dynamixel_driver.cpp: In member function ‘bool DynamixelDriver::readRegister(uint8_t, uint16_t, uint16_t, uint32_t*, const char**)’:
/home/ijnek/tmp_workspaces/dynamixel_control_ws/src/dynamixel-workbench/dynamixel_workbench_toolbox/src/dynamixel_workbench_toolbox/dynamixel_driver.cpp:776:11: warning: ISO C++ forbids variable length array ‘data_read’ [-Wvla]
  776 |   uint8_t data_read[length];
      |           ^~~~~~~~~
/home/ijnek/tmp_workspaces/dynamixel_control_ws/src/dynamixel-workbench/dynamixel_workbench_toolbox/src/dynamixel_workbench_toolbox/dynamixel_driver.cpp: In member function ‘bool DynamixelDriver::syncWrite(uint8_t, uint8_t*, uint8_t, int32_t*, uint8_t, const char**)’:
/home/ijnek/tmp_workspaces/dynamixel_control_ws/src/dynamixel-workbench/dynamixel_workbench_toolbox/src/dynamixel_workbench_toolbox/dynamixel_driver.cpp:1012:11: warning: ISO C++ forbids variable length array ‘multi_parameter’ [-Wvla]
 1012 |   uint8_t multi_parameter[4*data_num_for_each_id];
      |           ^~~~~~~~~~~~~~~
---

I accidentally closed #363, so this is an identical PR to that.

[ijnek]

Ping @ROBOTIS-Will , thanks!

[ROBOTIS-Will]

@ijnek
Thanks for the contribution!

[ijnek]

Thanks @ROBOTIS-Will