Clearer separation of lower level control

[chenyenru]

Problem Statement

According to InspirationRobotics/robosub_2023#64 (comment):

• pix_standalone.py (lower level) and robot_control.py (higher level) have overlaps
  • the controls they do need to be separated more

Approach Suggested

• separate the controls in pix_standalone.py and robot_control.py
• provide estimates of positions / orientations for the sub on the low level