Implement cookbook to manage Redis Cluster

• We may derive this from the existing chef recipe.
• However, since our current recipe manages redis.conf indirectly through gitlab.rb, it may be simpler to write a new recipe that directly manages redis.conf. Doing so would change (simplify) the way we currently manage redis instances and would let us skip the overhead of having to update omnibus to add more pass-through configuration settings for gitlab-ctl reconfigure to copy from gitlab.rb to redis.conf.
• While omnibus already ships with such a binary, it's Redis 6.2. We want Redis 7.0, as it includes many improvements related to Redis Cluster. Thus, it may make sense to build our own packages.
• Whichever approach we choose, this task should give us a chef recipe for creating redis-cluster nodes.

Result

New cookbook is available at gitlab-redis-cluster.