Don't rely on automatic conversion from array to first element

[sothawo]

Spring Data Elasticsearch currently relies on an automatic conversion from a collection to the first object in that collection, for example when reading a constructor parameter from the return of a scripted field. This automatic conversion will be removed from the spring-data-commons library, so we need to add the functionality in Spring Data Elasticsearch.

See spring-projects/spring-data-commons@23ad2f0