* telemetry: split webhook-processed hook registration out of NewTelemetryService
NewTelemetryService used to register a notifier processed-hook on the inner
*telemetryService directly. That made it impossible for downstream wrappers
(e.g. cloud's TelemetryService that overrides Webhook to fan out to a v3
observability pipeline) to intercept webhook events without double-firing
the legacy emission.
Lift the registration into a new exported helper RegisterWebhookHook, and
have the standalone server's wire provider createTelemetryService call it
right after construction so behavior is unchanged for callers that don't
wrap the service.
