Support `return_embedding` param in DocumentStore's `get_document_by_id`

[tstadel]

Is your feature request related to a problem? Please describe. BaseDocumentStore's get_all_documents supports return_embedding as method param but get_document_by_id does not. This is inconsistent and a bit confusing.

Describe the solution you'd like Add return_embedding param to get_doucment_by_id of BaseDocumentStore and all its subclasses.

Describe alternatives you've considered None

Additional context Besides API consistency this could be handy if you want to check whether an individual document has (correct) embeddings.