Fix EZP-23163: Use the new ConfigurationProcessor in kernel

> https://jira.ez.no/browse/EZP-23163

This PR *migrates* current configuration parsers for EzPublishCoreBundle to use the new `ConfigurationProcessor` and `Contextualizer` (see #931).

Parsers are now *stored* in a main `ConfigParser` which acts as a proxy and is passed to the `ConfigurationProcessor`.

## TODO
* [x] Implement new main configuration parser
* [x] Change implementation for all existing configuration parsers
* [x] Implement new ConfigurationProcessor in LegacyBundle
Yes, this is what is recommended in their doc.