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/cmLinkLineDeviceComputer.h

@@ -6,7 +6,6 @@
 #include "cmConfigure.h" // IWYU pragma: keep
 
 #include <string>
-#include <vector>
 
 #include "cmLinkLineComputer.h"
 
@@ -15,8 +14,6 @@ class cmGeneratorTarget;
 class cmLocalGenerator;
 class cmOutputConverter;
 class cmStateDirectory;
-template <typename T>
-class BT;
 
 class cmLinkLineDeviceComputer : public cmLinkLineComputer
 {