src: close HandleWraps instead of deleting them in OnGCCollect()

When all strong `BaseObjectPtr`s to a `HandleWrap` are gone, we
should not delete the `HandleWrap` outright, but instead close
it and then delete it only once the libuv close callback has been
called.

Based on the valgrind output from the issue below, this has a
good chance of fixing it.

Fixes: nodejs#39036

src/base_object-inl.h

@@ -201,7 +201,7 @@ void BaseObject::decrease_refcount() {
   unsigned int new_refcount = --metadata->strong_ptr_count;
   if (new_refcount == 0) {
     if (metadata->is_detached) {
-      delete this;
+      OnGCCollect();
     } else if (metadata->wants_weak_jsobj && !persistent_handle_.IsEmpty()) {
       MakeWeak();
     }

src/handle_wrap.cc

@@ -85,7 +85,16 @@ void HandleWrap::Close(Local<Value> close_callback) {
 
 
 void HandleWrap::OnGCCollect() {
-  Close();
+  // When all references to a HandleWrap are lost and the object is supposed to
+  // be destroyed, we first call Close() to clean up the underlying libuv
+  // handle. The OnClose callback then acquires and destroys another reference
+  // to that object, and when that reference is lost, we perform the default
+  // action (i.e. destroying `this`).
+  if (state_ != kClosed) {
+    Close();
+  } else {
+    BaseObject::OnGCCollect();
+  }
 }