Refactor arm and elevator to use the same class

[moreheadm]

254 has a class that they use for single motor subsystems https://github.com/Team254/FRC-2024-Public/blob/main/src/main/java/com/team254/lib/subsystems/ServoMotorSubsystem.java

Ideally we could combine arm and elevator into a class like this.

1. Come up with a good design.
2. Write the class.

Considerations:

1. Adjustable zeroing function.
2. Adjustable feedforward.
3. Ideally support different movement functions (i.e. motion magic, profiling on the roborio).

First iteration should just support current features though.