[RSDK-7322] Move analog writers from Board interface to Analog interface

[penguinland]

Everything compiles and the linter is happy, but that's as far as I've tested; I don't have an analog writer to try this out with. Olivia, maybe I could borrow one from you?

[github-actions]

Warning your change may break code samples. If your change modifies any of the following functions please contact @viamrobotics/fleet-management. Thanks!

component	function
base	IsMoving
board	GPIOPinByName
camera	Properties
encoder	Properties
motor	IsMoving
sensor	Readings
servo	Position
arm	EndPosition
audio	MediaProperties
gantry	Lengths
gripper	IsMoving
input_controller	Controls
movement_sensor	LinearAcceleration
power_sensor	Power
pose_tracker	Poses
motion	GetPose
vision	ClassificationsFromCamera

[oliviamiller]

lgtm, I don't have an analog writer but you could test with a fake board.

[penguinland]

I was unable to get the fake board to work. On closer inspection, it's because analogTestPin was the empty string, if you use any other pin it throws away any written value when you read it, and if you try to use that pin it complains that the pin can't be the empty string. So, I made the test pin "1", and then things work great (for this one pin; others continue throwing away the written values any time you try reading it). I still have doubts that having different behavior on analogTestPin is a good idea or that throwing away written values on any pin is a good idea, but those are questions for another day.