AK: Include utility from the STD if we aren't replacing STD

If we didn't define our own `move` and `forward` and inject it into the
`std` namespace, then we would error just after trying to `using` those,
if no one has included it before. Now, we will include `utility` from
the STD if we aren't replacing the `std`.

AK/StdLibExtras.h

@@ -45,6 +45,8 @@ constexpr T&& move(T& arg)
 }
 
 }
+#else
+#include <utility>
 #endif
 // clang-format on