OpenTelemetry Operator: ServiceMonitor bearerTokenFile reads arbitrary local file and sends contents as bearer auth

The OpenTelemetry Operator is a Kubernetes Operator for the OpenTelemetry Collector. Prior to 0.152.0, cmd/otel-allocator TargetAllocator instances with targetAllocator.prometheusCR.enabled set to true preserve a selected ServiceMonitor endpoint's bearerTokenFile value as HTTPClientConfig.Authorization.CredentialsFile. A tenant who can create or update a ServiceMonitor matched by serviceMonitorSelector and serviceMonitorNamespaceSelector can point bearerTokenFile at a file in the Collector pod, including /var/run/secrets/kubernetes.io/serviceaccount/token, and direct scraping to a tenant-controlled endpoint. The Collector reads that file at scrape time and sends its contents as bearer authorization on every scrape interval. Exploitation also requires the Collector service-account token or another sensitive file to be mounted and the Collector to reach the chosen target. The DenyFSAccessThroughSMs control was absent, allowing disclosure of the Collector's service-account JWT or other mounted files, and resulting Kubernetes API impact is limited by the Collector service account's permissions. This issue is fixed in version 0.152.0.