Rewrite conversion of top-level collections in MappingRedisConverter

[mp911de]

MappingRedisConverter.write(…) attempts to obtain an entity from the given object to later on decide how to serialize it (collection, map, …). PersistentEntity retrieval breaks if the type is encapsulated (e.g. Arrays.asList(…)). The code still attempts to obtain a keyspace and the identifier accessor.

We should generally avoid identifier, keyspace name, and TTL retrieval from a collection as collections do not have such a property.