Automate the Envoy AI gateway creation

<!-- Please only use this template for submitting enhancement requests --> **What would you like to be added**: Right now, we need to apply the envoy ai gateway manually following the https://github.com/InftyAI/llmaz/tree/main/docs/examples/envoy-ai-gateway, however, we need to create all these stuff automatically by introducing a controller. Also the configurations are static, once the service is down, the ai gateway is unaware of this, this is not right. **Why is this needed**: * Easy to setup * Dynamically change the envoy configurations based on the status of the services. **Completion requirements**: This enhancement requires the following artifacts: - [ ] Design doc - [ ] API change - [ ] Docs update The artifacts should be linked in subsequent comments.