[Feature][llm_agent] Enhance llm_agent to support team like behavior

### **Overview**
We need to enhance the `llm.agent` model to support team relationships between agents. This will allow one agent to have a team of other agents working under it, while team member agents can be used by multiple team leader agents. This mode is available in [llm_agent](https://github.com/apexive/odoo-llm/tree/16.0/llm_agent) module

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### **Current Behavior**
Currently, the `llm.agent` model exists as independent entities without any hierarchical or team-based relationships between them. Each agent operates independently with its own configuration.

The solution needs to be discussed in terms of technical changes, UI/UX, etc first before implementation.