Remove all "cluster vs not cluster" logic

[jesusgn90]

Wazuh	Elastic	Rev
3.x	6/7	n/a

Blocked by: wazuh/wazuh#3400

Description

The app has a lot of logic based on the cluster status, it overloads the app and the user experience itself. Most errors related to a status change of the cluster would be eradicated if Wazuh is always a cluster.

Proposal

Wait for wazuh/wazuh#3400, because it's blocking this change. Once it's implemented, we can safely remove all the logic related to the cluster status.

Some changes would be:

• Remove all API calls pointing to /manager/* endpoints.
• Remove/simplify all the logic using .getClusterInfo().
• Remove/simplify all logic using /cluster/status endpoint.
• Take care of [1st iteration] Move API credentials to the config.yml file #1465, because it'd be easier than right now.