Refactoring in encoded motors: defer mutex unlocking, better checking of sign bits

[penguinland]

Still haven't licked the main bug we're working on, but here is some refactoring that I've wanted to do since opening this file. Feel free to say "Alan, this can come after we've found the bug in GoFor, do it later."

Also feel free to say "don't create the sign function, do it this other way instead."

[randhid]

Alan, I like these changes. Go ahead.

[github-actions]

Package	Line Rate	Health
go.viam.com/rdk/components/arm	59%	➖
go.viam.com/rdk/components/arm/universalrobots	12%	❌
go.viam.com/rdk/components/arm/xarm	2%	❌
go.viam.com/rdk/components/arm/yahboom	7%	❌
go.viam.com/rdk/components/audioinput	55%	➖
go.viam.com/rdk/components/base	68%	➖
go.viam.com/rdk/components/base/agilex	62%	➖
go.viam.com/rdk/components/base/boat	41%	❌
go.viam.com/rdk/components/base/wheeled	76%	✅
go.viam.com/rdk/components/board	69%	➖
go.viam.com/rdk/components/board/arduino	10%	❌
go.viam.com/rdk/components/board/commonsysfs	47%	❌
go.viam.com/rdk/components/board/fake	39%	❌
go.viam.com/rdk/components/board/numato	19%	❌
go.viam.com/rdk/components/board/pi	50%	➖
go.viam.com/rdk/components/camera	66%	➖
go.viam.com/rdk/components/camera/fake	67%	➖
go.viam.com/rdk/components/camera/ffmpeg	72%	✅
go.viam.com/rdk/components/camera/transformpipeline	80%	✅
go.viam.com/rdk/components/camera/videosource	56%	➖
go.viam.com/rdk/components/encoder/fake	77%	✅
go.viam.com/rdk/components/gantry	68%	➖
go.viam.com/rdk/components/gantry/multiaxis	84%	✅
go.viam.com/rdk/components/gantry/oneaxis	86%	✅
go.viam.com/rdk/components/generic	85%	✅
go.viam.com/rdk/components/gripper	82%	✅
go.viam.com/rdk/components/input	85%	✅
go.viam.com/rdk/components/input/gpio	87%	✅
go.viam.com/rdk/components/motor	82%	✅
go.viam.com/rdk/components/motor/dmc4000	69%	➖
go.viam.com/rdk/components/motor/fake	60%	➖
go.viam.com/rdk/components/motor/gpio	64%	➖
go.viam.com/rdk/components/motor/gpiostepper	55%	➖
go.viam.com/rdk/components/motor/tmcstepper	66%	➖
go.viam.com/rdk/components/movementsensor	67%	➖
go.viam.com/rdk/components/movementsensor/cameramono	39%	❌
go.viam.com/rdk/components/movementsensor/gpsnmea	37%	❌
go.viam.com/rdk/components/movementsensor/gpsrtk	28%	❌
go.viam.com/rdk/components/posetracker	88%	✅
go.viam.com/rdk/components/sensor	88%	✅
go.viam.com/rdk/components/sensor/ultrasonic	31%	❌
go.viam.com/rdk/components/servo	77%	✅
go.viam.com/rdk/config	77%	✅
go.viam.com/rdk/control	57%	➖
go.viam.com/rdk/data	78%	✅
go.viam.com/rdk/grpc	25%	❌
go.viam.com/rdk/ml	67%	➖
go.viam.com/rdk/ml/inference	70%	✅
go.viam.com/rdk/motionplan	71%	✅
go.viam.com/rdk/operation	93%	✅
go.viam.com/rdk/pointcloud	71%	✅
go.viam.com/rdk/protoutils	62%	➖
go.viam.com/rdk/referenceframe	78%	✅
go.viam.com/rdk/registry	88%	✅
go.viam.com/rdk/resource	85%	✅
go.viam.com/rdk/rimage	78%	✅
go.viam.com/rdk/rimage/depthadapter	94%	✅
go.viam.com/rdk/rimage/transform	73%	✅
go.viam.com/rdk/rimage/transform/cmd/extrinsic_calibration	67%	➖
go.viam.com/rdk/robot	93%	✅
go.viam.com/rdk/robot/client	79%	✅
go.viam.com/rdk/robot/framesystem	68%	➖
go.viam.com/rdk/robot/impl	80%	✅
go.viam.com/rdk/robot/server	58%	➖
go.viam.com/rdk/robot/web	61%	➖
go.viam.com/rdk/robot/web/stream	87%	✅
go.viam.com/rdk/services/armremotecontrol	75%	✅
go.viam.com/rdk/services/armremotecontrol/builtin	25%	❌
go.viam.com/rdk/services/baseremotecontrol	75%	✅
go.viam.com/rdk/services/baseremotecontrol/builtin	71%	✅
go.viam.com/rdk/services/datamanager	62%	➖
go.viam.com/rdk/services/datamanager/builtin	81%	✅
go.viam.com/rdk/services/datamanager/datacapture	34%	❌
go.viam.com/rdk/services/datamanager/datasync	70%	➖
go.viam.com/rdk/services/motion	68%	➖
go.viam.com/rdk/services/motion/builtin	89%	✅
go.viam.com/rdk/services/navigation	54%	➖
go.viam.com/rdk/services/sensors	78%	✅
go.viam.com/rdk/services/sensors/builtin	97%	✅
go.viam.com/rdk/services/shell	15%	❌
go.viam.com/rdk/services/slam	86%	✅
go.viam.com/rdk/services/slam/builtin	73%	✅
go.viam.com/rdk/services/vision	82%	✅
go.viam.com/rdk/services/vision/builtin	74%	✅
go.viam.com/rdk/spatialmath	85%	✅
go.viam.com/rdk/subtype	96%	✅
go.viam.com/rdk/utils	71%	✅
go.viam.com/rdk/vision	26%	❌
go.viam.com/rdk/vision/chess	80%	✅
go.viam.com/rdk/vision/delaunay	87%	✅
go.viam.com/rdk/vision/keypoints	92%	✅
go.viam.com/rdk/vision/objectdetection	83%	✅
go.viam.com/rdk/vision/odometry	60%	➖
go.viam.com/rdk/vision/odometry/cmd	0%	❌
go.viam.com/rdk/vision/segmentation	49%	❌
go.viam.com/rdk/web/server	26%	❌
Summary	66% (19041 / 28716)	➖