Allow injecting a password for Redis Clusters

Most redis clusters will be using a password, and we need to make sure the operator has the capability to use password.

There are a few spots now where we will need the password.

* Readiness & Liveness Probes
* Redis node communication (we need to inject into the redis.conf)
* Redis clients need to use the password

We also need to provide this capability by providing a secret with interfaced keys.

This allows people using the Operator to inject secrets to Redis cluster however they prefer, whether this is via the External Secrets Operator or normal Kubernetes secret. Their applications can then use that same secret to connect to the Redis Cluster.