Retrieve Redis caching instance credentials from Vault

What

In Reconciler, retrieve Redis caching credentials under existing service secrets path runway_redis/$RUNWAY_REGION/* stored in #352 (closed). Context: https://docs.runway.gitlab.com/reference/blueprints/redis/#connect-to-an-instance.

We also need to retrieve the Redis AUTH secret and the CA cert for TLS connectivity (in-transit encryption).

Why

For allowing Runway services to connect to Redis caching instances.