Migrate the Databricks connector's test-connection off the legacy test_connection_steps helper onto the declarative @check / ChecksProvider / ErrorPack framework.

Scope:

• Replace the DatabricksConnection.test_connection override with a checks() provider driven by BaseConnection.test_connection.
• Implement all 13 seeded steps (CheckAccess gate + GetDatabases/GetSchemas/GetTables/GetViews/GetQueries/GetViewDefinitions/GetCatalogTags/GetSchemaTags/GetTableTags/GetColumnTags/GetTableLineage/GetColumnLineage), preserving the DatabricksEngineWrapper for catalog-scoped listing.
• Add a Databricks ErrorPack (token/permission/object-not-found tokens) folding in the shared network pack, with a TCP preflight in the gate.
• Add the 7 missing greenfield members to the shared DatabaseStep enum.
• Mark CheckAccess as ConnectionGate in the seeded JSON.
• Colocated unit test.