Split DutyCycleEncoder/AnalogEncoder into 2 classes

[ThadHouse]

DutyCycleEncoder as it currently exists is generally the wrong choice for users. It adds rollover support in addition to offset and conversion functionalities. But the rollover support can sometimes be problematic, and can create issues when the user doesn't need it. And generally the user doesn't need rollover support. We should move the rollover support into its own class.

[Starlight220]

Not sure about DutyCycle, but isn't AnalogPotentiometer the class the user usually wants?

[ThadHouse]

Closed by #6398