[Validator] Added option for specifying the size format for the File validator

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | yes and no, as the current calculation is not consistent
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10648
| License       | MIT
| Doc PR        | -

This lets someone choose between binary (multiples of 1024) and decimal (multiple of 1000) formats for specifying the size.

Example:

```php
use Symfony\Component\Validator\Constraints as Assert;

class Curriculum
{
    /**
     * @Assert\File(size=2000, sizeFormat="decimal")
    */
    public $file;
}
```

By default, the size format is in binary.