[libcxx][modularisation] moves <utility> content out of <type_traits>

Moves:

* `std::move`, `std::forward`, `std::declval`, and `std::swap` into
  `__utility/${FUNCTION_NAME}`.
* `std::swap_ranges` and `std::iter_swap` into
  `__algorithm/${FUNCTION_NAME}`

Differential Revision: https://reviews.llvm.org/D103734

NOKEYCHECK=True
GitOrigin-RevId: 6adbc83ee9e46b476e0f75d5671c3a21f675a936
diff --git a/include/__tree b/include/__tree
index b599a04..5f9ba8b 100644
--- a/include/__tree
+++ b/include/__tree
@@ -11,6 +11,7 @@
 #define _LIBCPP___TREE
 
 #include <__config>
+#include <__utility/forward.h>
 #include <algorithm>
 #include <iterator>
 #include <memory>