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/Step2/Exercise2.cmake

@@ -0,0 +1,51 @@
+cmake_minimum_required(VERSION 3.23)
+
+
+function(FilterFoo OutVar)
+# TODO3: Search all the variables in the argument list passed to FilterFoo,
+#        and place those containing "Foo" into the list named by "OutVar"
+
+  set(${OutVar} ${${OutVar}} PARENT_SCOPE)
+endfunction()
+
+
+
+# Testing for the above
+function(check_contains var)
+  if(NOT var IN_LIST OutList)
+    message(WARNING "OutList does not contain: ${var}")
+    set(Failed True PARENT_SCOPE)
+  endif()
+endfunction()
+
+function(check_nonfoo)
+  list(FILTER ARGN EXCLUDE REGEX Foo)
+  if(NOT ARGN STREQUAL "")
+    message(WARNING "OutList contains extra item(s): ${ARGN}")
+    set(Failed True PARENT_SCOPE)
+  endif()
+endfunction()
+
+if(SKIP_TESTS)
+  return()
+endif()
+
+set(InList FooBar BarBaz FooBaz BazBar QuxFoo BazQux)
+
+FilterFoo(OutList ${InList})
+
+if(NOT DEFINED OutList)
+  message("FilterFoo unimplemented or does nothing")
+  return()
+endif()
+
+set(Failed False)
+
+check_contains(FooBar)
+check_contains(FooBaz)
+check_contains(QuxFoo)
+check_nonfoo(${OutList})
+
+if(NOT Failed)
+  message("Success!")
+endif()