Introduce a resolver for Confluence resource references

The resource reference type parser module parses and resolves confluence resource references, but it so happens that it would be useful to be able to use this parsing and resolving code outside of them, for example in a script that replaces them with a regular resource reference.
We therefore introduce a new API for this: the org.xwiki.contrib.confluence.resolvers.resource.ConfluenceResourceReferenceResolver interface.