Add function accurateCastOrNull.

**Use case**
This function is needed to implement #10266

**Describe the solution you'd like**
The function is like `cast` but always returns nullable type and returns NULL if the casted value is not representable in the target type.

Example:

```
accurateCastOrNull(-1, 'UInt8')
NULL

cast(-1, 'UInt8')
255
```