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

Some headers were renamed, but others were split.

hal/src/main/native/sim/CANAPIInternal.hpp

@@ -0,0 +1,11 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// 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.
+
+#pragma once
+
+#include "wpi/hal/Types.h"
+
+namespace wpi::hal::can {
+int32_t GetCANModuleFromHandle(HAL_CANHandle handle, int32_t* status);
+}  // namespace wpi::hal::can