filemanager: add event-based update of attributes.

[mmalenic]

Instead of updating attributes via a PATCH request, the attributes would ideally be updated using the event bus in order to better control mutable access to the filemanager database. The API would ideally be read-only, and if it can PATCH, the attributes should probably be append-only, rather than supporting the full set of JSON patch operations.

This may require saving requested attribute updates in the filemanager database asynchronously, as it's possible that not all S3 events will have arrived when the event to update attributes is received. This could also be an opportunity to introduce some of the features discussed in https://github.com/umccr/orcabus/blob/docs/filemanager-linking/lib/workload/stateless/stacks/filemanager/docs/ATTRIBUTE_LINKING.md.