[ADT] Fix iplist_impl - use after move warnings (PR43943)

As detailed on PR43943, we're seeing static analyzer use after move warnings in the iplist_impl move constructor/operator as they call std::move to both the TraitsT and IntrusiveListT base classes.

As suggested by @dexonsmith this patch casts the moved value to the base classes to silence the warnings.

Differential Revision: https://reviews.llvm.org/D74062

llvm/include/llvm/ADT/ilist.h

@@ -198,10 +198,12 @@ class iplist_impl : public TraitsT, IntrusiveListT {
   iplist_impl &operator=(const iplist_impl &) = delete;
 
   iplist_impl(iplist_impl &&X)
-      : TraitsT(std::move(X)), IntrusiveListT(std::move(X)) {}
+      : TraitsT(std::move(static_cast<TraitsT &>(X))),
+        IntrusiveListT(std::move(static_cast<IntrusiveListT &>(X))) {}
   iplist_impl &operator=(iplist_impl &&X) {
-    *static_cast<TraitsT *>(this) = std::move(X);
-    *static_cast<IntrusiveListT *>(this) = std::move(X);
+    *static_cast<TraitsT *>(this) = std::move(static_cast<TraitsT &>(X));
+    *static_cast<IntrusiveListT *>(this) =
+        std::move(static_cast<IntrusiveListT &>);
     return *this;
   }