[Validator] Moved DoctrineCache to Doctrine Bridge

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

As per @stof remark on https://github.com/symfony/symfony/pull/9892 the `DoctrineCache` class should be located in the Doctrine Bridge.