[Selections] Refactor ValueListServiceImpl

Class org.onehippo.forge.selection.repository.valuelist.ValueListServiceImpl is responsible for populating any Selections fields shown in the Visual Editor in channel manager.

This class ignores any registered valuelist providers, and instead it manually traverses JCR nodes and creates a Valuelist POJO. This class is not aware that we now use resourcebundles, so when reading these JCR nodes, it expects they represent a Valuelist document, not a resourcebundle. Thus it fails to populate any Selections drop down fields in Visual Editor.