[wpilib] Move motor controllers to motorcontrol package (#3302)

Also deprecate SpeedController in favor of motorcontrol.MotorController and
SpeedControllerGroup in favor of motorcontrol.MotorControllerGroup.

The MotorController interface is derived from the SpeedController interface
so that code such as SpeedController x = new VictorSP(1) continues to
compile (just with a warning).

SpeedControllerGroup and MotorControllerGroup are independent classes;
both implement the MotorController interface.

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/subsystems/DriveSubsystem.h

@@ -6,7 +6,6 @@
 
 #include <frc/ADXRS450_Gyro.h>
 #include <frc/Encoder.h>
-#include <frc/PWMSparkMax.h>
 #include <frc/drive/MecanumDrive.h>
 #include <frc/geometry/Pose2d.h>
 #include <frc/geometry/Rotation2d.h>
@@ -14,6 +13,7 @@
 #include <frc/kinematics/ChassisSpeeds.h>
 #include <frc/kinematics/SwerveDriveKinematics.h>
 #include <frc/kinematics/SwerveDriveOdometry.h>
+#include <frc/motorcontrol/PWMSparkMax.h>
 #include <frc2/command/SubsystemBase.h>
 
 #include "Constants.h"
@@ -51,7 +51,7 @@ class DriveSubsystem : public frc2::SubsystemBase {
   void ResetEncoders();
 
   /**
-   * Sets the drive SpeedControllers to a power from -1 to 1.
+   * Sets the drive MotorControllers to a power from -1 to 1.
    */
   void SetModuleStates(wpi::array<frc::SwerveModuleState, 4> desiredStates);