Allow UNIQUE and PRIMARY KEY to be specified on the same column

[fulghum]

Related to: dolthub/dolt#7395

[jycor]

LGTM!

It seems like MySQL also allows multiple unique keys to be defined over the same column(s), and just ignores the duplicates
Not sure if it's worth adding in this PR though.

mysql> create table t (id int unique key unique key);
Query OK, 0 rows affected (0.0259 sec)

mysql> show create table t;
+-------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                            |
+-------+-----------------------------------------------------------------------------------------------------------------------------------------+
| t     | CREATE TABLE `t` (
  `id` int DEFAULT NULL,
  UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+-------+-----------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.0012 sec)

[fulghum]

whoa... good find on the duplicate key options! Very weird that MySQL allows that. I'll go ahead and add support for that while I'm in here since it's only a couple more lines of code and some new test statements. Thank you!