ISPN-8865 Converted the LuceneCacheLoader to utilise the Publisher based API instead of process, however the feature-packs were not updated to reflect this, therefore it's necessary for the `org.infinispan.lucene-directory` module to add the following deps:

        <module name="io.reactivex.rxjava2.rxjava" slot="@infinispan.module.slot@"/>
        <module name="org.reactivestreams.reactive-streams" slot="@infinispan.module.slot@"/>