Change metadata-only deposits protocol to add a metadata-provenance url

Decide what property to use for the metadata-provenance url: <swh:metadata-provenance>
!280 (closed), !281 (closed): Check existence of property on metadata-only deposits
!277 (closed): Recommend on using it in the documentation
Extend the deposit receipt to reply with a warning when not using this property (could also be useful for other stuff, like when using deprecated formats/fields like the Slug header instead of <swh:deposit>)
!284 (closed), !348 (closed): Extend deposit cli(s) to warn when not using this property

Migrated from T3935 (view on Phabricator)