EG does not cleanup Envoy proxy deployments if a gateway delete notification is missed

*Description*:
The issue observed is that orphaned Envoy proxy deployments are not removed when a gateway delete notification is missed.

It is expected that during a full reconcile, EG can identify and clean up these orphaned proxies to maintain consistency and prevent resource leakage. finalizers are missing.

*Repro steps*:
1. Create a gateway and observe that the Envoy proxy deployment is created successfully.
2. Scale EG to 0 and delete the gateway resource
3. Scale EG back to 1 to force a full reconcile
4. Observe that the orphaned Envoy proxy deployment is not removed.