Rename shadowed local variables

In a similar effort to f01592f91, here we mostly rename shadowed local
variables to remove the warnings produced when compiling with
-Wshadow=compatible-local.

This fixes 63 warnings and leaves just 5.

Author: Justin Pryzby, David Rowley
Reviewed-by: Justin Pryzby
Discussion https://postgr.es/m/20220817145434.GC26426%40telsasoft.com

src/backend/partitioning/partbounds.c

@@ -4321,11 +4321,11 @@ get_qual_for_range(Relation parent, PartitionBoundSpec *spec,
 		PartitionDesc pdesc = RelationGetPartitionDesc(parent, false);
 		Oid		   *inhoids = pdesc->oids;
 		int			nparts = pdesc->nparts,
-					i;
+					k;
 
-		for (i = 0; i < nparts; i++)
+		for (k = 0; k < nparts; k++)
 		{
-			Oid			inhrelid = inhoids[i];
+			Oid			inhrelid = inhoids[k];
 			HeapTuple	tuple;
 			Datum		datum;
 			bool		isnull;

src/backend/partitioning/partprune.c

@@ -2289,11 +2289,10 @@ match_clause_to_partition_key(GeneratePruningStepsContext *context,
 		elem_clauses = NIL;
 		foreach(lc1, elem_exprs)
 		{
-			Expr	   *rightop = (Expr *) lfirst(lc1),
-					   *elem_clause;
+			Expr	   *elem_clause;
 
 			elem_clause = make_opclause(saop_op, BOOLOID, false,
-										leftop, rightop,
+										leftop, lfirst(lc1),
 										InvalidOid, saop_coll);
 			elem_clauses = lappend(elem_clauses, elem_clause);
 		}