[sim] Move Sim classes from HAL to wpilibc/j (#2549)

Also move some things in HAL for consistency.

WAS:
C++:
- C APIs: #include "mockdata/AccelerometerData.h"
- User side class: #include "simulation/AccelerometerSim.h"
Java:
- JNI APIs: hal.sim.mockdata.AccelerometerData (and a few classes in hal.sim)
- User side classes: hal.sim.AccelerometerSim

IS:
C++:
- C APIs: #include "hal/simulation/AccelerometerData.h"
- C++ class: #include "frc/simulation/AccelerometerSim.h"
Java:
- JNI APIs: hal.simulation.AccelerometerData
- User side class: wpilibj.simulation.AccelerometerSim

hal/src/main/native/sim/mockdata/RoboRioDataInternal.h

@@ -7,8 +7,8 @@
 
 #pragma once
 
-#include "mockdata/RoboRioData.h"
-#include "mockdata/SimDataValue.h"
+#include "hal/simulation/RoboRioData.h"
+#include "hal/simulation/SimDataValue.h"
 
 namespace hal {
 class RoboRioData {