[Cluster by default] Update cluster pages

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Docu epic
https://github.com/wazuh/wazuh-documentation/issues/5212

Description

These are the two main changes that the cluster will undergo in https://github.com/wazuh/wazuh-documentation/issues/5212:

• Some configuration options in the ossec.conf are removed and others are changed.
• The cluster is always running, can't be disabled and shouldn't be stopped (as other important services).

Those changes should be reflected in the cluster sections of the documentation:

• User manual - Configuring cluster
• Development - Cluster

[Selutario]

Status update

This is how our cluster documentation looks like right now:

Personally, I find it a bit strange that the explanation of how to configure a cluster is done in the index. In any case, there is no standard for this in our doc: some pages have no index, others just a summary, and others like the cluster have important explanations in it.

Then, in the Basics section, we show general info about the cluster but in my opinion, we go too deep in explaining how it works and the tasks it performs (Agent info, Integrity thread, etc). On the one hand, because we are duplicating what is already explained in the Cluster section in Development. On the other hand, because I don't think these details are of much interest to normal users.

I'm wondering if it might make more sense for the index to just include a summary of what is discussed in this section. Next, there would be 3 pages within the cluster section:

• Cluster formation: This page would combine what is currently in Basics (leaving only the essentials) and the cluster configuration info.
• Agents connections: Would remain unchanged.
• Cluster management: It doesn't contain very useful info right now but at the moment I wouldn't know where to put it either.

I am making these changes to see if the goal of improving this section's organization and making it easier for users to configure the cluster would be met.