Basic compose file for testing OTEL tracing

Signed-off-by: Christopher Petito <47751006+krissetto@users.noreply.github.com>

hack/otel/compose.yaml

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+name: moby-otel
+
+services:
+
+  jaeger:
+    image: jaegertracing/all-in-one:latest
+    ports:
+      - 16686:16686
+
+  aspire-dashboard:
+    image: mcr.microsoft.com/dotnet/nightly/aspire-dashboard
+    ports:
+      - 18888:18888
+    environment:
+      DOTNET_DASHBOARD_UNSECURED_ALLOW_ANONYMOUS: 'true'
+  
+  otelcol:
+    image: otel/opentelemetry-collector:latest
+    restart: always
+    depends_on:
+      - jaeger
+      - aspire-dashboard
+    ports:
+      - 4318:4318 # default otlp http port
+    volumes:
+      # Mount the otelcol.yml config file
+      - ./otelcol.yaml:/etc/otelcol/config.yaml

hack/otel/otelcol.yaml

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+# Receive signals over gRPC and HTTP
+# moby currently uses http
+receivers:
+  otlp:
+    protocols:
+      grpc:
+      http:
+
+exporters:
+  otlp/jaeger:
+    endpoint: jaeger:4317
+    tls::insecure: true
+  otlp/aspire:
+    endpoint: aspire-dashboard:18889
+    tls::insecure: true
+
+service:
+  pipelines:
+    traces:
+      receivers: [otlp]
+      exporters: [otlp/jaeger, otlp/aspire]

hack/otel/usage.md

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+# Sample stack for testing OTEL functionality with moby
+
+To easily test the OTEL functionality present in moby, you can spin up a small demo compose stack that includes:
+- an OTEL collector container;
+- a Jaeger container to visualize traces;
+- an alternative Aspire Dashboard container to visualize traces;
+
+The OTEL collector is configured to export Traces to both the Jaeger and Aspire containers.
+
+The `hack/otel` directory contains the compose file with the services configured, along with a basic configuration file for the OTEL collector.
+
+## How can I use it?
+
+1) Export the env var used to override the OTLP endpoint:  
+  `export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318` (if running in a devcontainer or in other ways, you might have to change how you pass this env var to the daemon);
+2) Start the moby engine you want to get traces from (make sure it gets the env var declared above);
+3) Start the otel compose stack by running `docker compose up -d` in the `hack/otel/` directory;
+4) Make some calls to the engine using the Docker CLI to send some traces to the endpoint;
+5) Browse Jaeger at `http://localhost:16686` or the Aspire Dashboard at `http://localhost:18888/traces`;
+6) To see some traces from the engine, select `dockerd` in the top left dropdown
+
+> **Note**: The precise steps may vary based on how you're working on the codebase (buiding a binary and executing natively, running/debugging in a devcontainer, etc... )
+
+## Cleanup?
+
+Simply run `docker compose down` in the `hack/otel/` directory.
+
+You can also run `unset OTEL_EXPORTER_OTLP_ENDPOINT` to get rid of the OTLP env var from your environment