Resolve notification email templates by a tenant/workflow/type/suffix cascade

Resolves an Easy Email notification template with a Drupal-suggestion-style cascade, most specific first, over the instance tenant, the workflow, the notification type, and an optional suffix:

orchestra_<tenant>_<workflow>_<type>_<suffix>
orchestra_<tenant>_<workflow>_<type>
orchestra_<tenant>_<type>_<suffix>
orchestra_<tenant>_<type>
orchestra_<workflow>_<type>_<suffix>
orchestra_<workflow>_<type>
orchestra_<type>_<suffix>
orchestra_<type>
orchestra_generic

Empty dimensions are skipped, first existing wins (one query). The tenant comes from ProcessInstance::getTenantId(), so per-tenant (e.g. per-domain) templates need no wiring; the suffix from an orchestra_notification_template_suffix process variable in the event context. Backward compatible with the previous chain.