Panic when using latin1 charset and latin1_german1_ci collation

[timsehn]

Referencing example in: #4168

I decided to define the collations on the columns instead so I could test. This time it panics.

Repro:

MySQL [charsets_collations]> create table german1 (c char(10) CHARACTER SET latin1 COLLATE latin1_german1_ci);
Query OK, 0 rows affected (0.003 sec)

MySQL [charsets_collations]> create table german2 (c char(10) CHARACTER SET latin1 COLLATE latin1_german2_ci);
Query OK, 0 rows affected (0.002 sec)

MySQL [charsets_collations]> create table german3 (c char(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci);
Query OK, 0 rows affected (0.004 sec)

MySQL [charsets_collations]> INSERT INTO german1 VALUES ('Bar'), ('Bär');
Query OK, 2 rows affected (0.004 sec)

MySQL [charsets_collations]> INSERT INTO german2 VALUES ('Bar'), ('Bär');
Query OK, 2 rows affected (0.004 sec)

MySQL [charsets_collations]> INSERT INTO german3 VALUES ('Bar'), ('Bär');
Query OK, 2 rows affected (0.003 sec)

MySQL [charsets_collations]> SELECT * FROM german1 WHERE c = 'Bär';
ERROR 1105 (HY000): panic in ExchangeIterPartitionRows: runtime error: invalid memory address or nil pointer dereference
MySQL [charsets_collations]> show create table german1;
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table   | Create Table                                                                                                                                            |
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
| german1 | CREATE TABLE `german1` (
  `c` char(10) CHARACTER SET latin1 COLLATE latin1_german1_ci
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin |
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.001 sec)

MySQL [charsets_collations]> SELECT * FROM german1 WHERE c = 'Bär';
ERROR 1105 (HY000): panic in ExchangeIterPartitionRows: runtime error: invalid memory address or nil pointer dereference
MySQL [charsets_collations]> SELECT * FROM german2 WHERE c = 'Bär';
ERROR 1105 (HY000): panic in ExchangeIterPartitionRows: runtime error: invalid memory address or nil pointer dereference
MySQL [charsets_collations]> SELECT * FROM german3 WHERE c = 'Bär';
+------+
| c    |
+------+
| Bar  |
| Bär  |
+------+
2 rows in set (0.001 sec)

[Hydrocharged]

The issue here is that CREATE TABLE does not properly block not-yet-implemented collations. This has been fixed in dolthub/go-mysql-server#1215

[Hydrocharged]

Additionally, the above PR adds the latin1 character set, along with the following collations:

• latin1_bin
• latin1_general_ci
• latin1_general_cs
• latin1_german1_ci
• latin1_german2_ci
• latin1_swedish_ci