[FrameworkBundle] Fixed validator factory definition when the Validator API is "auto" for PHP < 5.3.9

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11580
| License       | MIT
| Doc PR        | -
this BC layer does not work for people passing ``auto`` explicitly.

You need to transform ``auto`` into the appropriate value in a ``beforeNormalization`` call on the node.

And for the default value, IMO, the right solution is to set the default value according to the PHP version rather than using a ``validate`` call to set a default value when there is no value