coloring common IMU functions and change default max bulk param in dynamixel workbench to 21

[tzf230201]

recently I worked with build-in IMU on the openCR board,
coloring some common functions will be very helpful during the debugging process

[tzf230201]

I changed the max bulk parameter from 20 to 21 because most humanoid kid-size (20 dof) robot projects in the world use openCR as their sub-controller, like me too.

for some reason, I shouldn't change my dynamixel protocol from 1.0 to 2.0, so couldn't use the sync read function, and was forced to use bulk read instead.

because the maximum parameter in the addBulkReadParam function is limited by

if (bulk_read_parameter_cnt_ <(MAX_BULK_PARAMETER-1))

then only 19 servos can take advantage of this bulk read.

I think changing the maximum bulk parameter from 20 to 21 will be of great help to people on humanoid projects.

then I also found a typo in the error message as well as the bulk param that was added exceeding the limit.

previously written "Too many bulk parameter are added (default buffer size is 10)"

even though the dynamixel_driver.h file sets the default buffer size to 20

#define MAX_BULK_PARAMETER 20

because I changed the max bulk param to 21, so I changed the error message to
"Too many bulk parameters are added (default buffer size is 21)".

[ROBOTIS-Will]

Hi @tzf230201 Thank you for your contribution :)
We'll review your PR and merge it. This may take a couple weeks.
Thank you!