[wpilib] Deprecate MotorController

The drive classes no longer need this interface, and it rigidly couples
us to motor controller vendors who only update and do a major release of
their vendordep once per year.

We were originally going to do this in wpilibsuite#6053, but we wanted to gather
feedback on the alternate approach during a season first (as far as I
know, we received none).

wpilibc/src/main/native/include/frc/motorcontrol/MotorController.h

@@ -11,7 +11,8 @@ namespace frc {
 /**
  * Interface for motor controlling devices.
  */
-class MotorController {
+class [[deprecated(
+    "This class is being removed with no replacement")]] MotorController {
  public:
   virtual ~MotorController() = default;
 

wpilibj/src/main/java/edu/wpi/first/wpilibj/motorcontrol/MotorController.java

@@ -6,7 +6,12 @@
 
 import edu.wpi.first.wpilibj.RobotController;
 
-/** Interface for motor controlling devices. */
+/**
+ * Interface for motor controlling devices.
+ *
+ * @deprecated This class is being removed with no replacement.
+ */
+@Deprecated(forRemoval = true, since = "2025")
 public interface MotorController {
   /**
    * Common interface for setting the speed of a motor controller.