Add an e2e test that: 1. Exposes EPP metrics based on [this guide](https://gateway-api-inference-extension.sigs.k8s.io/guides/metrics/). 2. Generates traffic through the EPP to the [backend LLM](https://gateway-api-inference-extension.sigs.k8s.io/guides/#deploy-sample-model-server). 3. Scrapes the [metrics](https://gateway-api-inference-extension.sigs.k8s.io/guides/metrics/#exposed-metrics) supported by EPP.