Improve Redis support

[jerbob92]

Proposal

The Redis support is a little outdated and does not support the following functionality:

• ACL support, because you can't give it a username
• Sentinel support

My proposal is to update go-redis v6.15.9 to v8.11.4 to support ACL in Redis 6+ and implement scalers for Redis Sentinel.

Use-Case

ACL

Redis added ACL in Redis 6: to make use of this, the client also needs to support this, which has been added in later versions of go-redis. Updating the client and allowing to pass a username to the scalers will solve this.

Sentinel

Our cluster uses Redis Sentinel, we use HAProxy now to point to the master server, but it's not perfect.
go-redis supports Sentinel out of the box so we just need a way to pass metadata/authentication to support it.

Anything else?

With this change, total Redis support will come to 6 scalers:

• Redis Lists
• Redis Streams
• Redis Cluster Lists
• Redis Cluster Streams
• Redis Sentinel Lists
• Redis Sentinel Streams

The code is really similar and mostly in the same files. When adding the Sentinel support, I tried to make it as much in line with the current codebase, see #2181, however, this could probably be just 1 scaler right? Difference between the different scalers is minimal and we can easily add metadata to decide whether it's standalone, cluster or sentinel and lists or streams.

[zroubalik]

@jerbob92 we can close this one, right?

[jerbob92]

@zroubalik Yep :)