IWYU: Update for Debian 13 CI job

`include-what-you-use` diagnostics, in practice, are specific to
the environment's compiler and standard library.  Update includes
to satisfy IWYU for our CI job under Debian 13.  Some patterns:

* Types named in virtual `override` signatures no longer require
  includes since the overridden signature already names them.

* A function argument's type needs to be included even if its constructor
  is called only by implicit conversion.  For example, constructing a
  `std::function` from a lambda now requires `<functional>`.

* Some prior mysterious `<type_traits>` inclusions are no longer required.

Source/cmFastbuildNormalTargetGenerator.cxx

@@ -6,6 +6,7 @@
 #include <algorithm>
 #include <array>
 #include <cstddef>
+#include <functional>
 #include <iterator>
 #include <map>
 #include <sstream>
@@ -21,7 +22,6 @@
 
 #include "cmsys/FStream.hxx"
 
-#include "cmAlgorithms.h"
 #include "cmCommonTargetGenerator.h"
 #include "cmCryptoHash.h"
 #include "cmFastbuildTargetGenerator.h"