Made config filename configurable

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | tbd

A use case: In routing bundle, we need `cmf_routing.persistence.phpcr.enabled = true` for PHPCR tests and `cmf_routing.persistence.orm.enabled true` for ORM tests. You can't enable both of them.