demo-apps: metrics_counter, redis_streams

[andrussal]

This PR adds the third set of example applications to logos-blockchain-testing:

• metrics_counter
• redis_streams

These examples extend the set into cases that depend more on surrounding systems than on the application node alone.

Review note

These example PRs do not need critical review. The goal is to get useful example integrations into the repo and improve them from there.

What this PR covers

• metrics_counter covers Prometheus-backed checks and extra-service wiring
• redis_streams covers a Redis-based workflow with consumer groups and failover-style behavior

This PR extends the example set into monitoring-oriented and backend-driven cases.

Integration shape

Each app is split into four parts:

• App or service — the code under test
• TF integration — the code that connects the app to TF
• Workloads and expectations — reusable behavior and checks
• Example binaries — small programs that run one sample scenario