Tutorial: Rewrite using conventions enabled by CMake 3.23

This is a full re-write of the CMake Tutorial for CMake 3.23, both
the functionality it provides, as well as the modern workflows that
developers use when interfacing with CMake.

Issue: #22663, #23086, #23799, #26053, #26105, #26153, #26914

Help/guide/tutorial/Step4/Tutorial/Tutorial.cxx

@@ -0,0 +1,36 @@
+// A simple program that computes the square root of a number
+#include <format>
+#include <iostream>
+#include <string>
+
+#include <MathFunctions.h>
+
+#ifdef TUTORIAL_USE_VENDORLIB
+#  include <Vendor.h>
+#endif
+
+int main(int argc, char* argv[])
+{
+  if (argc < 2) {
+    std::cout << std::format("Usage: {} number\n", argv[0]);
+    return 1;
+  }
+
+  int unused;
+
+  // convert input to double
+  double const inputValue = std::stod(argv[1]);
+
+  // calculate square root
+  double const outputValue = mathfunctions::sqrt(inputValue);
+  std::cout << std::format("The square root of {} is {}\n", inputValue,
+                           outputValue);
+
+#ifdef TUTORIAL_USE_VENDORLIB
+  if (CheckSqrt(inputValue, outputValue)) {
+    std::cout << "Sqrt verified by vendor\n";
+  } else {
+    std::cout << "Sqrt rejected by vendor\n";
+  }
+#endif
+}