Render a general_settings.coordination_redis block into the litellm-helm
proxy config when the bundled Redis is enabled, gated on a new
redis.coordination.enabled value and skipped when the user already
supplies their own block. Sentinel deployments render sentinel_nodes and
service_name rather than a host/port pair.
Also fixes litellm.redis.serviceName, which gated its sentinel branch on
standalone architecture. The bundled Redis subchart only serves sentinel
in replication mode, and renders no master Service there, so REDIS_HOST
pointed at a Service that never existed for every sentinel user.
Documents the coordination redis in the componentized chart and in the
terraform modules, whose existing REDIS_* exports now feed it directly.
Adds helm-unittest coverage for both charts' redis wiring, which had none
