[Validator] BIC country code validation

**Description**  
The BIC validator only checks that the country code is a 2 letters string.

If `symfony/intl` component is available, the validator should check that the country code is valid.

I can submit a PR if you want.

**Example**  
For instance `ASPKAT2LXXX` is valid and `ASPKAA2LXXX` is not as there is no `AA` country code. But both strings pass the validator test.
