Conformance Echo Server Depends on Ingress Controller Conformance Repo

[robscott]

What happened:
Any time we need to tweak our base image for conformance tests we have to update https://github.com/kubernetes-sigs/ingress-controller-conformance, which is largely frozen in time other than our updates to the base image.

What you expected to happen:
We should likely control the image within Gateway API repo.

I think it would be relatively simple to set this up since we already have a job that builds and pushes images. Our cloudbuild.yaml calls make release-staging:

gateway-api/Makefile

Lines 156 to 158 in 18506b7

	.PHONY: release-staging
	release-staging: image.multiarch.setup
	hack/build-and-push.sh

That calls out to hack/build-and-push.sh which already builds and pushes multiple images, including our Istio-based echo-server:

gateway-api/hack/build-and-push.sh

Lines 68 to 92 in 18506b7

	echo "Building and pushing admission-server image...${BUILDX_PLATFORMS}"
	# First, build the image, with the version info passed in.
	# Note that an image will *always* be built tagged with the GIT_TAG, so we know when it was built.
	# And, we add an extra version tag - either :latest or semver.
	# The buildx integrate build and push in one line.
	docker buildx build \
	-t ${REGISTRY}/admission-server:${GIT_TAG} \
	-t ${REGISTRY}/admission-server:${VERSION_TAG} \
	--build-arg "COMMIT=${COMMIT}" \
	--build-arg "TAG=${BINARY_TAG}" \
	--platform ${BUILDX_PLATFORMS} \
	--push \
	-f docker/Dockerfile.webhook \
	.
	echo "Building and pushing echo-server image...${BUILDX_PLATFORMS}"
	docker buildx build \
	-t ${REGISTRY}/echo-server:${GIT_TAG} \
	-t ${REGISTRY}/echo-server:${VERSION_TAG} \
	--platform ${BUILDX_PLATFORMS} \
	--push \
	-f docker/Dockerfile.echo \
	.