string comparison ignores `NUL` character by default

In MySQL, string comparisons just ignore the `NUL` character (`'\0'`)

```sql
mysql> select '123' = '123\0';
+-----------------+
| '123' = '123\0' |
+-----------------+
| 1 |
+-----------------+
1 row in set (0.0003 sec)
```

```sql
mysql> select '123' = '\01\02\03\0';
+-----------------------+
| '123' = '\01\02\03\0' |
+-----------------------+
| 1 |
+-----------------------+
1 row in set (0.0004 sec)
```

The `NUL` characters still impact the length of the string
```sql
mysql> select length('\01\02\03\0');
+-----------------------+
| length('\01\02\03\0') |
+-----------------------+
| 7 |
+-----------------------+
1 row in set (0.0004 sec)
```

It's likely that this is a default collation issue.
We see this behavior when using `utf8mb4_0900_ai_ci` and `utf8mb4_unicode_ci`, but not `utf8mb4_0900_bin`.
```sql
mysql> select '123' collate utf8mb4_0900_ai_ci = '123\0' collate utf8mb4_0900_ai_ci;
+-----------------------------------------------------------------------+
| '123' collate utf8mb4_0900_ai_ci = '123\0' collate utf8mb4_0900_ai_ci |
+-----------------------------------------------------------------------+
| 1 |
+-----------------------------------------------------------------------+
1 row in set (0.0004 sec)

mysql> select '123' collate utf8mb4_unicode_ci = '123\0' collate utf8mb4_unicode_ci;
+-----------------------------------------------------------------------+
| '123' collate utf8mb4_unicode_ci = '123\0' collate utf8mb4_unicode_ci |
+-----------------------------------------------------------------------+
| 1 |
+-----------------------------------------------------------------------+
1 row in set (0.0004 sec)
```

```sql
mysql> select '123' collate utf8mb4_0900_bin = '123\0' collate utf8mb4_0900_bin;
+-------------------------------------------------------------------+
| '123' collate utf8mb4_0900_bin = '123\0' collate utf8mb4_0900_bin |
+-------------------------------------------------------------------+
| 0 |
+-------------------------------------------------------------------+
1 row in set (0.0004 sec)
```

This behavior extends to tables
```sql
mysql> create table t (c char(10) primary key) collate utf8mb4_0900_ai_ci;
Query OK, 0 rows affected (0.0126 sec)

mysql> insert into t values ('123');
Query OK, 1 row affected (0.0028 sec)

mysql> insert into t values ('\01\02\03\0');
ERROR: 1062: Duplicate entry '' for key 't.PRIMARY'

mysql> select * from t where c = '\01\02\03\0';
+-----+
| c |
+-----+
| 123 |
+-----+
1 row in set (0.0005 sec)
```

```sql
mysql> create table t (c char(10) primary key) collate utf8mb4_0900_bin;
Query OK, 0 rows affected (0.0125 sec)

mysql> insert into t values ('123');
Query OK, 1 row affected (0.0027 sec)

mysql> insert into t values ('\01\02\03\0');
Query OK, 1 row affected (0.0019 sec)

mysql> select * from t where c = '\01\02\03\0';
+---------+
| c |
+---------+
| 1 2 3 |
+---------+
1 row in set (0.0005 sec)
```

The `utf8mb4_0900_ai_ci` and `utfmb4_unicode_ci` collations do not work as expected in dolt.

Note: By default, PostgreSQL does not ignore `NUL` character