Add shared haf-app-test-runner image for HAF application testing

Problem

Three HAF application repos maintain nearly identical docker/ci/Dockerfile files:

• balance_tracker
• reputation_tracker
• haf_block_explorer

Each builds a custom ci-runner image for DinD-based testing. This causes:

• Duplicated maintenance effort
• Inconsistent environments across projects
• Per-project image build overhead in CI

Proposal

Create a shared haf-app-test-runner image in common-ci-configuration that all HAF apps can use.

Requirements Analysis

Common to all projects:

• docker-builder base (Alpine + Docker for DinD)
• JMeter + m2u (from benchmark-test-runner)
• Python 3.12+ with pip
• py3-psycopg2
• postgresql-client
• bash, ca-certificates
• openjdk11-jre (for JMeter)

Additional from balance_tracker (recommended for all):

• gcc, musl-dev, python3-dev, linux-headers (build Python wheels)
• gcompat, libstdc++ (glibc compat for pre-built wheels like hiveio-wax)
• util-linux (proper flock for NFS - BusyBox flock fails on NFS mounts)

Migration Plan

Phase 1: Create shared image in common-ci-configuration

1. Add haf-app-test-runner/Dockerfile to common-ci-configuration
2. Add CI job to build and publish the image
3. Tag initial release

Phase 2: Migrate projects (can be done incrementally)

For each project:

1. Update .gitlab-ci.yml to use the shared image
2. Remove docker/ci/Dockerfile
3. Remove docker-ci-runner-build job from CI
4. Test that all CI jobs pass

Order of migration:

1. reputation_tracker (simplest)
2. haf_block_explorer
3. balance_tracker

Benefits

• Single maintenance point: Update deps once, all projects benefit
• Faster CI: No per-project image build step
• Consistency: All HAF apps use identical test environment
• Easier onboarding: New HAF apps just use the shared image

Open Questions

1. Should we version the image or use :latest?
2. Image naming: haf-app-test-runner vs haf-test-runner?

See proposed Dockerfile in haf_block_explorer: docs/shared-ci-runner-plan.md