feat(byoo-perf): add OTLP sink and telemetrygen load generation

[shobham-nv]

TL;DR

Adds load generation and an in-cluster OTLP sink to the BYOO collector performance suite, and wires perf run end-to-end. run now deploys a sink, deploys the authentic collector with its export redirected at that sink, and drives telemetrygen load at the selected profile's rates before cleaning up. Stacked on #623.

Additional Details

The suite must drive real telemetry through the collector and let it drain, otherwise the collector backs up against the unreachable placeholder export endpoints and the numbers are meaningless. This PR adds the two building blocks and the wiring:

• pkg/sink — a stock collector-contrib sink that accepts OTLP over gRPC (4317) and HTTP (4318), discards payloads via the debug exporter, exposes its otelcol_receiver_accepted_* counters on a Prometheus telemetry endpoint (8888), and gates readiness with health_check (13133). This is the destination the collector under test exports to.
• pkg/loadgen — single-shot telemetrygen Jobs (one per enabled signal, backoffLimit: 0 so a retry never replays load) that send OTLP into the collector receiver at the profile's rates for warmup + window.
• pkg/labels — shared labels so deploy, sink, and loadgen tag objects identically and cleanup stays scoped.
• pkg/deploy — DeploySink, RunLoad (create + wait for completion), an export-credentials Secret that backs the collector's /etc/byoo-otel-collector/secrets volume (so the generated ${file:...} exporter config resolves and the collector can actually start), and Cleanup extended to also remove jobs, config maps, and secrets.
• run redirects export via Provider=OTEL_COLLECTOR + endpoints pointed at the sink; new flags --sink-image, --loadgen-image, --skip-load.

Limitations / to validate on a cluster

• End-to-end startup was not run against a live cluster from here. The exporter-credentials + secrets-volume override and the sink/telemetrygen image tags are the first things to confirm on a real cluster.
• Measurement and reporting are the next milestone; the sink already exposes its receiver counters for it to read.

For the Reviewer

• Closest look: pkg/deploy/deploy.go (credentials Secret + mountSecretOverPath, RunLoad, broadened Cleanup) and cmd/perf/main.go runShape.
• Sink/loadgen image defaults are stock upstream images and overridable via flags.

For QA

• make perf-test (build + vet + unit tests, cluster-free) passes.
• Manual end-to-end (perf run --shape container) should be exercised against a target cluster.

Issues

NO-REF

Checklist

• I am familiar with the Contributing Guidelines.
• I have signed off my commits for Developer Certificate of Origin (DCO) compliance.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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