Fix motor groups not properly setting motor gearing/encoder units

[SprintKeyz]

Summary:

Appended _all to the set_gearing and set_encoder_units calls in the motor group constructor.

Motivation:

After testing, it seems that when creating a motor group, the gearing you provide to the constructor only applies to the first motor in the group. Previously, the constructor would call set_gearing and pass in only the gearset, which would result in the index argument defaulting to 0 and therefore only applying to the first motor. The same is true with the existing set_encoder_units call. Changing these to their _all variants means all motors in the group will get the proper gearing and encoder units.

Example:

pros::MotorGroup motors({1, 2}, pros::MotorGears::blue); will only set the first motor to blue.

Test Plan:

• Create a motor group, being sure to specify a gearing and encoder units
• Call get_gearing_all on the motor group and print the values to verify the gearing is correct
• Similarly, call get_encoder_units_all on the motor group and print the values to verify the encoder units are correct

[SprintKeyz]

Fixed in #611