Local Avro Schema Store should be shared and dynamic

When a DTO like the BulkStatus evolves with new fields the Avro schema is also updated.

When using a shared Avro Schema store like Confluent Schema registry we have backward/forward compatibility, this means that old consumers can read records from new producers and new consumers can read records from old producers.

When using the default Avro Schema store, schemas are located in NUXEO_DATA/avro directory. When this folder contains the old and new schema definition the compatibility is ensured.

A new deployment that keeps the directory content will be able to consume old records while producing new records.

But old consumers will not be able to read the new records unless the schema is added to its local store and the instance restarted because schemas are only loaded on start.

This must be fixed so that unknown schema are always fetched to disk.

This way when the Avro schema store directory is shared among nodes we have backward/forward compatibility.