[WCM] [Validator] Added DateTimeRangeValidator

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes (symfony/symfony#9164)
| Applies to    | 2.4+
| Fixed tickets | 

This adds a new validator to verify if a DateTime is between an optional min or max. Essentially, it is the Range validator for DateTime.