Reasonable defaults for Lawnmower SITL

[slgrobotics]

Solved Problem

When running '''make px4_sitl gz_lawnmower_lawn``` the vehicle completes the mission, but its movements aren't smooth.

To fix that, RD_* parameters must be adjusted in the airframe definition file.

Ammends #{23430}

Solution

Speed, accelerations and turn rate were adjusted.

also, it looks like with Units being rad, the upper limit for RD_TRANS_DRV_TRN and RD_TRANS_TRN_DRV parameters should be in radians too.

Test coverage

Running '''make px4_sitl gz_lawnmower_lawn``` produces smooth movements.

[chfriedrich98]

Very nice, thanks for taking care of that!