Use CmmnHistoryManager when deleting case instances through CMMN deployment cascade

The cascade path in CaseDefinitionEntityManagerImpl previously called
CmmnHistoryHelper.deleteHistoricCaseInstance directly, bypassing the
cmmnHistoryManager.recordHistoricCaseInstanceDeleted hook. Custom
history managers (e.g. composite managers subscribing to cleanup
events) were silently skipped when a deployment was cascade-deleted,
diverging from the BPMN equivalent in
ExecutionEntityManagerImpl.deleteProcessInstanceCascade.

Mirror BPMN's structure: move the per-instance deletion logic into
DefaultCmmnHistoryManager.recordHistoricCaseInstanceDeleted,
recursing to this for sub-cases. The cascade caller now invokes the
manager hook directly. The static
CmmnHistoryHelper.deleteHistoricCaseInstance is removed since all its
callers are gone; bulkDeleteHistoricCaseInstances is unchanged (its
entry points already go through the manager hook).