PG-260: Fix display of queries in pg_stat_monitor view.

Don't display queries in PARSE or PLAN state, to keep it consistent
with previous behavior, this avoids showing intermediate scripts like
part of a procedure, such as:
$1
$1 := $3

pg_stat_monitor.c

@@ -1712,6 +1712,11 @@ pg_stat_monitor_internal(FunctionCallInfo fcinfo,
 			if (tmp.state == PGSS_FINISHED)
 				continue;
 		}
+
+		/* Skip queries such as, $1, $2 := $3, etc. */
+		if (tmp.state == PGSS_PARSE || tmp.state == PGSS_PLAN)
+			continue;
+
 		if (tmp.info.parentid != UINT64CONST(0))
 		{
 			int len = 0;