Move To Mouth: getting stuck in error cases

[atharva-kashyap]

If the robot tries to move to the user's mouth and fails (because it collides with the user's mouth), then user gets stuck (because there is no recourse). Both options (go back/continue) require the arm to not be in collision.

[amalnanavati]

ada_feeding#128 and #94 should partially solve this, because the "resume"/"retry" action will be MoveToMouth which will disable wheelchair collisions. However, the Back option will still be MoveToStagingConfiguration, which expects the robot to be out-of-collision. To address this, I should add a MoveFromMouthToStagingConfiguration motion that is called when the user clicks "Back" from MoveToMouth