Remove deprecated aliases

[apdavison]

1.0 is the point to remove the aliases retained through 0.x:

• fairgraph/fields.py: the whole module (Field, renamed to Property)
• registry.py: the fields, field_names, required_field_names and existence_query_fields classmethods, and Node (now NodeMeta)
• base.py: RepresentsSingleObject (now Releasable)
• embedded.py: EmbeddedMetadata (now KGEmbedded), and its re-export from fairgraph/__init__.py
• the scope keyword handled by handle_scope_keyword (utility.py), across 11 signatures and 14 call sites. Its warning already promises removal in 1.0.

Care: queries.py imports EmbeddedMetadata, LinkedMetadata and Node from openminds.base. Those are upstream openMINDS classes, not fairgraph's aliases, and must not be touched.

The release notes will need a migration guide for each removed name.