Add RangeTableEntryFromNSItem macro

addRangeTableEntryXXX methods return a ParseNamespaceItem with pg >= 13.
RangeTableEntryFromNSItem macro is added so that we return the range
table entry from the ParseNamespaceItem in pg>=13 and for pg < 13 rte
would already be returned with addRangeTableEntryXXX methods.

Commit on Postgres side:
5815696bc66b3092f6361f53e0394909647042c8

src/backend/distributed/executor/insert_select_executor.c

@@ -346,9 +346,8 @@ WrapSubquery(Query *subquery)
 
 	/* create range table entries */
 	Alias *selectAlias = makeAlias("citus_insert_select_subquery", NIL);
-	RangeTblEntry *newRangeTableEntry = addRangeTableEntryForSubquery(pstate, subquery,
-																	  selectAlias, false,
-																	  true);
+	RangeTblEntry *newRangeTableEntry = RangeTableEntryFromNSItem(addRangeTableEntryForSubquery(
+		pstate, subquery, selectAlias, false, true));
 	outerQuery->rtable = list_make1(newRangeTableEntry);
 
 	/* set the FROM expression to the subquery */

src/include/distributed/version_compat.h

@@ -40,6 +40,7 @@
 #define varoattno varattnosyn
 #define varnoold varnosyn
 #define Set_ptr_value(a,b) a->ptr_value = b
+#define RangeTableEntryFromNSItem(a) a->p_rte
 #else /* pre PG13 */
 #define lnext_compat(l, r) lnext(r)
 #define list_delete_cell_compat(l,c,p) list_delete_cell(l,c,p) 
@@ -50,6 +51,7 @@
 #define getOwnedSequencesCompat(a,b) getOwnedSequences(a,b)
 #define ExplainOnePlanCompat(a,b,c,d,e,f,g,h) ExplainOnePlan(a,b,c,d,e,f,g)
 #define Set_ptr_value(a,b) a->data.ptr_value = b
+#define RangeTableEntryFromNSItem(a) a
 #endif
 #if PG_VERSION_NUM >= PG_VERSION_12