XWIKI-19479: Add support for more than String values to event custom parameters

...stream-api/src/main/java/org/xwiki/eventstream/Event.java

...ain/java/org/xwiki/eventstream/internal/DefaultEvent.java

...iki/eventstream/query/AbstractPropertyQueryCondition.java

...va/org/xwiki/eventstream/query/CompareQueryCondition.java

...in/java/org/xwiki/eventstream/query/InQueryCondition.java

...in/java/org/xwiki/eventstream/query/SimpleEventQuery.java

.../java/org/xwiki/eventstream/query/SortableEventQuery.java

...java/org/xwiki/eventstream/internal/DefaultEventTest.java

...xwiki/eventstream/store/solr/internal/SolrEventStore.java

...xwiki/eventstream/store/solr/internal/EventStoreTest.java

...xwiki/mentions/internal/MentionsLegacyEventConverter.java

...wiki/mentions/internal/MentionsNotificationDisplayer.java