refactor(ocpp): use buildStatusNotificationRequest helper in TriggerMessage handlers

refactor(ocpp): use buildStatusNotificationRequest helper in TriggerMessage handlers

Replace inline StatusNotification payload construction in both OCPP 1.6
and 2.0 TriggerMessage handlers with the centralized
buildStatusNotificationRequest helper. Export the helper from
OCPPServiceUtils to make it available.

This eliminates 5 inline duplications of the same payload structure
that risked diverging from the single source of truth.