Separate Redis instrumentation per client/instance

What does this MR do?

This is the groundwork required for a series of improvements on Redis usage visualization.

It separates the instrumentation storages for each Redis client being used. These being, Cache, SharedState, Queues and Action Cable.

That means that these changes will make the following achievable:

• Separate Redis logs per Redis instance
• Categorize the Redis instance in Prometheus metrics
• Separate Redis performance bar data per Redis instance

In summary, here's what this MR does:

1. Transforms Gitlab::Instrumentation::Redis into an aggregation class. It conserves most of the interface, but instead reads from all defined storages
2. Moves the Gitlab::Instrumentation::RedisDriver method definitions to Gitlab::Instrumentation::RedisInterceptor module. That's mostly a decision discussed at gitlab-com/gl-infra/scalability#353 (closed) in order to avoid duplication of concerns and still instrument written/read bytes, timings and Redis calls in a single place (also it's a requirement to access the provided @options[:instrumentation_class]).
3. It instruments the Action Cable initializer to also use a separate storage (it's not being used at GitLab.com yet).

gitlab-com/gl-infra/scalability#353 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content