[wpilib] Add functional interface equivalents to MotorController (#6053)

This does not deprecate any current functionality, but prepares the way for future deprecation.

The drive classes now accept void(double) functions, which makes them more flexible.

The C++ API ended up a bit more verbose, but the Java API is really concise with method references, which is >80% of our userbase. For example:

`DifferentialDrive drive = new DifferentialDrive(m_leftMotor::set, m_rightMotor::set);`

Lambdas can be passed to interoperate with vendor motor controller APIs that don't have e.g., set(double), so CTRE doesn't have to maintain their WPI_ classes anymore.

MotorControllerGroup was replaced with PWMMotorController.addFollower() for PWM motor controllers. Users of CAN motor controllers should use their vendor's follower functionality.

wpilibc/src/test/native/cpp/motorcontrol/MotorControllerGroupTest.cpp

@@ -8,6 +8,7 @@
 #include <vector>
 
 #include <gtest/gtest.h>
+#include <wpi/deprecated.h>
 
 #include "motorcontrol/MockMotorController.h"
 
@@ -32,6 +33,8 @@ std::ostream& operator<<(std::ostream& os,
   return os;
 }
 
+WPI_IGNORE_DEPRECATED
+
 /**
  * A fixture used for MotorControllerGroup testing.
  */
@@ -124,3 +127,5 @@ TEST_P(MotorControllerGroupTest, StopMotor) {
 
 INSTANTIATE_TEST_SUITE_P(Tests, MotorControllerGroupTest,
                          testing::Values(TEST_ONE, TEST_TWO, TEST_THREE));
+
+WPI_UNIGNORE_DEPRECATED