twenty/v2.42.1: Put the record creation form back behind a feature flag (#26472)

Puts the record creation form back behind IS_RECORD_CREATION_FORM_ENABLED , removed in #25907 . With the flag off, creating a record is the pre-form behaviour again: the record is created immediately, then opened (side panel or record page, label identifier in edit mode) as before. Changes FeatureFlagKey.IS_RECORD_CREATION_FORM_ENABLED restored: shared enum, admin panel flag metadata, dev seed (on, so local dev and the e2e create-record spec keep using the form), generated front enums and the SDK metadata client.