[Observability] Deploy OpenTelemetry Collector and Parca/eBPF profiling backends #5369

Task Summary

Stand up the local deployment wiring that receives, stores, and visualizes telemetry, default-off and isolated from the application services.

• Add an OpenTelemetry Collector configuration and wire it into the single-node docker-compose stack.
• Store each signal in an external backend the Collector exports to: Loki (logs), VictoriaMetrics (metrics), Jaeger (traces), and Parca (profiles).
• Add Grafana as the dashboard layer, pre-provisioned with datasources for Loki, VictoriaMetrics, and Jaeger, so operators get log search, metric dashboards, and trace views with no Texera-built UI.
• Add the Parca server configuration and the Parca eBPF agent for continuous profiling.
• Make the observability backends opt-in through native COMPOSE_PROFILES in .env (one profile per signal), off by default, so a plain install runs only core Texera.
• Add configuration-validation specs for the collector and Parca config, and a README documenting the stack and how to point an external Grafana or OpenSearch at the same endpoints instead.
• The application runs unchanged whether or not these services are started.

Task Type

• DevOps / Deployment / CI
• Refactor / Cleanup
• Testing / QA
• Documentation
• Performance
• Other

Scope

Part of the observability effort, now scoped to instrumentation and export only; viewing is handled by Grafana and other external tools, not a Texera-built UI. Grafana and Loki are AGPLv3 optional operator-run components, not bundled in any Texera release artifact; the Collector, VictoriaMetrics, Jaeger, and Parca are Apache-2.0. The former in-repo query gateway and dashboard issues (#5370 to #5374) are closed.

Related

Part of #4070. Depends on #5368.