Use bitwise rotate functions in more places

There were a number of places in the code that used bespoke bit-twiddling
expressions to do bitwise rotation. While we've had pg_rotate_right32()
for a while now, we hadn't gotten around to standardizing on that. Do so
now. Since many potential call sites look more natural with the "left"
equivalent, add that function too.

Reviewed by Tom Lane and Yugo Nagata

Discussion:
https://www.postgresql.org/message-id/CAFBsxsH7c1LC0CGZ0ADCBXLHU5-%3DKNXx-r7tHYPAW51b2HK4Qw%40mail.gmail.com

src/backend/executor/nodeHash.c

@@ -1840,8 +1840,8 @@ ExecHashGetHashValue(HashJoinTable hashtable,
 		Datum		keyval;
 		bool		isNull;
 
-		/* rotate hashkey left 1 bit at each step */
-		hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+		/* combine successive hashkeys by rotating */
+		hashkey = pg_rotate_left32(hashkey, 1);
 
 		/*
 		 * Get the join attribute value of the tuple