Fix Memoize to work with partitionwise joining.

A couple of places weren't up to speed for this.  By sheer good
luck, we didn't fail but just selected a non-memoized join plan,
at least in the test case we have.  Nonetheless, it's a bug,
and I'm not quite sure that it couldn't have worse consequences
in other examples.  So back-patch to v14 where Memoize came in.

Richard Guo

Discussion: https://postgr.es/m/CAMbWs48GkNom272sfp0-WeD6_0HSR19BJ4H1c9ZKSfbVnJsvRg@mail.gmail.com

src/backend/optimizer/util/pathnode.c

@@ -4193,6 +4193,7 @@ do { \
 
 				FLAT_COPY_PATH(mpath, path, MemoizePath);
 				REPARAMETERIZE_CHILD_PATH(mpath->subpath);
+				ADJUST_CHILD_ATTRS(mpath->param_exprs);
 				new_path = (Path *) mpath;
 			}
 			break;