Too slow to convert to java from cpp

[aitazhixin]

There is a topic with type std_msgs/msg/Float32MultiArray. When the msg was received in APP, convert from cpp to java will spend 100ms. Because of array elements being convert to Float Object in java from c++ float. Why not generate Float32MultiArray with data type float[]?

[aitazhixin]

@esteve can you help to convert List to float[]?

[jacobperron]

@aitazhixin Is this PR relevant #165?