Add support for sameAs

[yarikoptic]

When --instance INSTANCE_NAME is provided, and that abbreviation is not matching the name prefix within identifier within what we load from dandiset.yaml record (e.g. identifier: DANDI:000003), we then go through sameAs entries, parse instances there and see if that INSTANCE_NAME is present -- and take the id associated with it. E.g. if --instance EMBER-DANDI and we have sameAs: ['dandi://ember-dandi/000001'] -- we upload to the 000001 of the EMBER-DANDI instance.