PostgreSQL compatibility: `^` evaluates as bitwise XOR instead of exponentiation

Split out from #22247.

### Mismatch

`^` evaluates as bitwise XOR instead of PostgreSQL exponentiation.

```sql
SELECT 2 ^ 3;
```

PostgreSQL:

```text
8
```

DataFusion:

```text
1
```

### Expected behavior

For PostgreSQL-compatible SQL semantics, DataFusion should either match PostgreSQL's result or raise the same class of domain/semantic error.
