sql: casts from integers to "char" do not match Postgres

Some examples in Postgres:

```
marcus=# SELECT 12345::INT2::"char";
char
------
1
(1 row)

marcus=# SELECT 12345::INT4::"char";
ERROR: 22003: "char" out of range
LOCATION: i4tochar, char.c:169

marcus=# SELECT 12345::INT8::"char";
char
------
1
(1 row)
```

In CRDB v22.2.6:

```
defaultdb> SELECT 12345::INT2::"char";
ERROR: "char" out of range
SQLSTATE: 22003

defaultdb> SELECT 12345::INT4::"char";
ERROR: "char" out of range
SQLSTATE: 22003

defaultdb> SELECT 12345::INT8::"char";
ERROR: "char" out of range
SQLSTATE: 22003
```

Jira issue: CRDB-27480