feat(observability): export uploader telemetry via BYOO OTLP

[kristinapathak]

Why

The request-trace-uploader needs its own operational telemetry through the workload-scoped BYOO Collector. A local Prometheus scrape endpoint is not the uploader telemetry contract.

Scope

• Replace the uploader-local Prometheus registry and /metrics endpoint with direct, signal-specific OTLP export for metrics.
• Export uploader structured logs directly through the signal-specific OTLP logs endpoint and protocol.
• Configure tracing from the signal-specific OTLP traces endpoint and protocol. Use W3C context propagation and bounded server spans for health endpoints, then upload-operation spans as those operations land.
• Use only OTEL_EXPORTER_OTLP_LOGS_ENDPOINT and OTEL_EXPORTER_OTLP_LOGS_PROTOCOL for logs, OTEL_EXPORTER_OTLP_METRICS_ENDPOINT and OTEL_EXPORTER_OTLP_METRICS_PROTOCOL for metrics, and OTEL_EXPORTER_OTLP_TRACES_ENDPOINT and OTEL_EXPORTER_OTLP_TRACES_PROTOCOL for traces. Support grpc, http, and http/protobuf.
• Do not use OTEL_EXPORTER_OTLP_ENDPOINT as a fallback. It can describe Collector outbound configuration rather than the workload-to-Collector path.
• Retain health-only /livez and /readyz endpoints. Rename the listener setting from METRICS_ADDR to HEALTH_ADDR.
• Export only finite metric attributes. Do not emit request payloads, credentials, paths, filenames, upload IDs, request IDs, NCA IDs, or error text as metric attributes, trace attributes, or log fields.
• Flush providers with a bounded timeout on SIGTERM. Export failures must not change readiness.

Tests

• Direct OTLP delivery tests for logs, traces, and metrics for every supported protocol.
• Unit tests for endpoint and protocol selection, W3C propagation, structured-log redaction, and bounded trace attributes.
• Metric-reader tests for uploader lifecycle and backlog metric names with finite attributes.
• NVCF integration coverage that proves the uploader receives signal-specific logs, metrics, and traces endpoint plus protocol for its workload-scoped BYOO Collector.

Non-goals

• A PodMonitor or Prometheus scrape path for uploader metrics.
• Sending request payload records through OTLP logs.

Parent: #1004