[wpilibc] Clean up integration tests (#3400)

The command and shuffleboard integration tests were removed because
their unit tests counterparts already provide adequate coverage. Java
already removed these.

wpilibcIntegrationTests/src/main/native/cpp/Main.cpp

@@ -0,0 +1,10 @@
+// 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.
+
+#include "gtest/gtest.h"
+
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}