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/Step8/MathFunctions/MathLogger/CMakeLists.txt

@@ -0,0 +1,6 @@
+add_library(MathLogger INTERFACE)
+
+target_sources(MathLogger
+  INTERFACE
+    FILE_SET HEADERS
+)

Help/guide/tutorial/Step8/MathFunctions/MathLogger/MathFormatting.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <string>
+
+namespace mathlogger {
+
+enum LogLevel
+{
+  INFO,
+  WARN,
+  ERROR,
+};
+
+inline std::string FormatLog(LogLevel level, std::string const& message)
+{
+  switch (level) {
+    case INFO:
+      return "INFO: " + message;
+    case WARN:
+      return "WARN: " + message;
+    case ERROR:
+      return "ERROR: " + message;
+  }
+  return "UNKNOWN: " + message;
+}
+
+}

Help/guide/tutorial/Step8/MathFunctions/MathLogger/MathLogger.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <string>
+
+#include "MathFormatting.h"
+#include "MathOutput.h"
+
+namespace mathlogger {
+
+struct Logger
+{
+  LogLevel level = INFO;
+
+  void SetLevel(LogLevel new_level) { level = new_level; }
+  void Log(std::string const& message)
+  {
+    std::string formatted = FormatLog(level, message);
+    WriteLog(formatted);
+  }
+};
+
+}

Help/guide/tutorial/Step8/MathFunctions/MathLogger/MathOutput.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <iostream>
+#include <string>
+
+namespace mathlogger {
+inline void WriteLog(std::string const& msg)
+{
+  std::cout << msg;
+}
+}