Add rock for net-istio-controller

[mvlassis]

Closes canonical/knative-operators#238

This rock is based on the image found here: https://console.cloud.google.com/gcr/images/knative-releases/global/knative.dev/net-istio/cmd/controller

To check that everything is as expected:

# Clone the repository and checkout to this branch, then cd to the proper subdirectory
cd net-istio-controller

# Build the rock
tox -e pack

# Export to docker
tox -e export-to-docker

# Sanity tests
tox -e sanity

# Compare output with the upstream image

docker run gcr.io/knative-releases/knative.dev/net-istio/cmd/controller:v1.12.3
## Sample output
## Output
2024/11/12 11:27:01 Error building kubeconfig: failed to create client config: invalid configuration: no configuration has been provided, try setting KUBERNETES_MASTER environment variable

docker run net-istio-webhook:v1.12.3
# Get the ID of the container
docker ps
# Run bash into it
docker exec -ti <container_id> bash
# Execute the service command manually
/ko-data/controller
## Sample output
# Output
2024/11/12 11:29:29 Error building kubeconfig: failed to create client config: invalid configuration: no configuration has been provided, try setting KUBERNETES_MASTER environment variable

[NohaIhab]

thank you @mvlassis , left you some comments for the code and will test in parallel as you address them.

[NohaIhab]

some additional comments based on the ko spec

[NohaIhab]

LGTM, thank you @mvlassis !