sql: fix integer math edge cases

The following edge cases differ in crdb and postgres:

```
SELECT 2 + 2 / 2 AS three;
-- postgres: 3
-- crdb: 3.0000000000000000000

SELECT (-2147483648)::int4 * (-1)::int4;
-- postgres: ERROR: integer out of range
-- crdb: 2147483648

SELECT (-2147483648)::int4 / (-1)::int4;
-- postgres: ERROR: integer out of range
-- crdb: 2147483648.0000000000

SELECT (-9223372036854775808)::int8 / (-1)::int8;
-- postgres: ERROR: bigint out of range
-- crdb: 9223372036854775808.0

SELECT (-9223372036854775808)::int4 / (-1)::int4;
-- postgres: ERROR: bigint out of range
-- crdb: 9223372036854775808.0

SELECT (-9223372036854775808)::int8 / (-1)::int2;
SELECT (-9223372036854775808)::int4 / (-1)::int4;
-- postgres: ERROR: bigint out of range
-- crdb: 9223372036854775808.0

select (1.5::float8)::int8;
-- postgres: 2
-- crdb: 1

select (-1.5::float8)::int8;
-- postgres: -2
-- crdb: -1
```

This was found in pg_regress int4 and int8.

Jira issue: CRDB-33891