[wpiutil] Add wpi::scope_exit (#4432)

This is based on std::scope_exit in the C++ library fundamentals TS v3.

wpiutil/src/test/native/cpp/ScopeExitTest.cpp

@@ -0,0 +1,36 @@
+// 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"
+#include "wpi/scope"
+
+TEST(ScopeExitTest, ScopeExit) {
+  int exitCount = 0;
+
+  {
+    wpi::scope_exit exit{[&] { ++exitCount; }};
+
+    EXPECT_EQ(0, exitCount);
+  }
+
+  EXPECT_EQ(1, exitCount);
+}
+
+TEST(ScopeExitTest, Release) {
+  int exitCount = 0;
+
+  {
+    wpi::scope_exit exit1{[&] { ++exitCount; }};
+    wpi::scope_exit exit2 = std::move(exit1);
+    wpi::scope_exit exit3 = std::move(exit1);
+    EXPECT_EQ(0, exitCount);
+  }
+  EXPECT_EQ(1, exitCount);
+
+  {
+    wpi::scope_exit exit{[&] { ++exitCount; }};
+    exit.release();
+  }
+  EXPECT_EQ(1, exitCount);
+}