Deprecate dataSource table with dual-write to workspace.databaseSchema (#19059)

## Summary
- Starts deprecation of the `core.dataSource` table by introducing a
dual-write system: `DataSourceService.createDataSourceMetadata` now
writes to both `core.dataSource` and `core.workspace.databaseSchema`
- Migrates read sites (`WorkspaceDataSourceService.checkSchemaExists`,
`WorkspaceSchemaFactory`, `MiddlewareService`,
`WorkspacesMigrationCommandRunner`) to read from
`workspace.databaseSchema` instead of querying the `dataSource` table
- Removes the unused `databaseUrl` field from `WorkspaceEntity` and
drops the column via migration
- Adds a 1.20 upgrade command to backfill `workspace.databaseSchema`
from `dataSource.schema` for existing workspaces

packages/twenty-server/src/engine/twenty-orm/entity-manager/workspace-entity-manager.spec.ts

@@ -256,6 +256,7 @@ describe('WorkspaceEntityManager', () => {
         IS_CONNECTED_ACCOUNT_MIGRATED: false,
         IS_GRAPHQL_QUERY_TIMING_ENABLED: false,
         IS_RECORD_TABLE_WIDGET_ENABLED: false,
+        IS_DATASOURCE_MIGRATED: false,
       },
       userWorkspaceRoleMap: {},
       eventEmitterService: {