Remove "slave" haproxy resources

[rurkss]

This PR removes the redis-slave-HAProxy, deeming it unnecessary and potentially dangerous .
Originally, this resource was designed as an endpoint for Redis replication nodes to connect to slave nodes of source cluster.
However, when replicated redis uses this resource, the sentinels on source side detect it as a potential slave for failover scenario. In failover, sentinels mistakenly treat the HAProxy pods as legitimate redis slaves and attempt to promote the HAProxy pod as the next master, as it is impossible to do, sentinels get stuck in a promotion loop.
Workaround is to use redis-slave-service as endpoint on source cluster. This way, when sentinels detect replicated redis as potential master in failover scenario, they will not be able to promote it, because replicated redis node is unreachable for connection and sentinels will forget this node.

[indiebrain]

We also want to capture some notes in the CHANGELOG informing consumers how upgrading to a version of the operator containing this change could affect their applications.

[indiebrain]

📦 🚀 🤖