Related to NE-1034, we should create E2E tests that confirm the functionality of Istio and sidecar injection with using Gateway API. This was defined previously as a stretch goal inside NE-1034.

The test should confirm:

1. Sidecars are not injected without explicitly setting the sidecar.istio.io/inject annotation
2. Sidecars are not injected in Gateway Deployment; despite sidecar.istio.io/inject being set to true (used for automatic deployments). OSSM doesn't support Automatic deployments at them moment, but regardless, a sidecar should not be injected.