MDEV-32090 Test for null-safe equals in join

This ticket is fixed by MDEV-32555 and this test captures a different use case.

mysql-test/main/subselect_nulls_innodb.result

+#
+# MDEV-32090 Index does not handle null-safe equals operator correctly in join
+#
+CREATE TEMPORARY TABLE t1 (
+`id` int(10) unsigned NOT NULL,
+`number` int(10) unsigned DEFAULT 0,
+`name` varchar(47) DEFAULT NULL,
+`street` mediumint(8) unsigned DEFAULT NULL,
+PRIMARY KEY (`id`),
+KEY `streetNumber` (`street`,`number`,`name`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_unicode_ci;
+INSERT INTO t1 (id, number, name, street) VALUES (100733476, 14, NULL, 1115569);
+SELECT
+b1.id
+FROM
+t1 b1
+INNER JOIN t1 b2 ON (
+b1.street = b2.street
+AND b1.number <=> b2.number
+AND b1.name <=> b2.name
+);
+id
+100733476
+DROP TABLE t1;
+#
+# End of 10.11 tests
+#

mysql-test/main/subselect_nulls_innodb.test

+--source include/have_innodb.inc
+
+--echo #
+--echo # MDEV-32090 Index does not handle null-safe equals operator correctly in join
+--echo #
+
+CREATE TEMPORARY TABLE t1 (
+  `id` int(10) unsigned NOT NULL,
+  `number` int(10) unsigned DEFAULT 0,
+  `name` varchar(47) DEFAULT NULL,
+  `street` mediumint(8) unsigned DEFAULT NULL,
+  PRIMARY KEY (`id`),
+  KEY `streetNumber` (`street`,`number`,`name`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_unicode_ci;
+
+INSERT INTO t1 (id, number, name, street) VALUES (100733476, 14, NULL, 1115569);
+
+SELECT
+    b1.id
+FROM
+    t1 b1
+    INNER JOIN t1 b2 ON (
+        b1.street = b2.street
+        AND b1.number <=> b2.number
+        AND b1.name <=> b2.name
+    );
+
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.11 tests
+--echo #