Update functions and tests after agent-groups changes

[Selutario]

Now all group assignment information is stored only in global.db. Agent-groups files (/var/ossec/queue/agent-groups/) no longer exist after changes made in:

• Migrate agent-group files to wazuh-db wazuh#10771

As a result, it is important to review and update all those functions and tests that interacted with queue/agent-groups/. It includes these files:

• add_agents_to_default_group: This script writes to the agent-groups files.
• test_authd_agents_ctx:
  • Files are created or deleted inside queue/agent-groups/ (on lines 136, 172)
  • Update docstrings.

There are some system tests which also need to be updated (test_integrity_sync, test_agent_files_deletion), but that's already being done in #2479.

[damarisg]

Duplicated by IT Authd/Wazuh DB: Refactor for failures caused by new development of Wazuh DB.