[hal] Consistently use .hpp for C++ header content

Some headers were renamed, but others were split.

hal/src/main/native/sim/mockdata/PowerDistributionData.cpp

@@ -2,8 +2,8 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-#include "../PortsInternal.h"
-#include "PowerDistributionDataInternal.h"
+#include "../PortsInternal.hpp"
+#include "PowerDistributionDataInternal.hpp"
 
 using namespace wpi::hal;