ci: wire v2/redis integration tests into CI pipeline

Parent Issue: #111 (closed)

Note

This MR is a follow up action for !497 (merged), please retarget to master after it is merged.

Adds three integration jobs covering supported Redis topologies:

• integration:redis (single-node)
• integration:redis:cluster
• integration:redis:sentinel

Topology setup is handled by small bash scripts under v2/redis/testdata/ci/.

I would have preferred to reuse our docker-compose files, which can be used to run these tests locally. However, setting the Cluster and Sentinel instance via scripts allows us to avoid messing with network_mode: host / DIND networking complexities.