Automation-controller: automation-controller: workflowjobnode.ancestor_artifacts lacks prevent_search, exposing no_log set_stats artifacts via orm-traversal count-oracle

A flaw was found in the Ansible Automation Platform automation-controller. The
WorkflowJobNode.ancestor_artifacts database column, which stores the raw merged set_stats
artifacts propagated between workflow nodes, is not wrapped in prevent_search() and is therefore
accepted for arbitrary field lookups by the REST filter backend, even though it is omitted from
the API serializer. Because the column is persisted before Ansible's no_log masking is applied,
a user with only read access to a workflow — or, via a regular-expression lookup that bypasses
the JSON cross-relation filter guard through the world-readable credential-types endpoint, any
authenticated user with no roles — can use the result count as a boolean/count oracle to recover,
character by character, secret values that a playbook author explicitly marked no_log, including
across organizations.