Allow any network to be provided to docker builder

[edwardthiele]

Under the Skaffold build configuration for docker, you can provide a network to connect the docker container (https://skaffold.dev/docs/references/yaml/#build-artifacts-docker-network), however you are restricted in terms of what network options can be set.

In particular, you cannot set network=cloudbuild, which can be helpful for auth reasons when running inside Google Cloud Build.

Expected behavior

You should be able to set network=cloudbuild and ideally any other network

Actual behavior

Validation fails when network=cloudbuild is set

[idsulik]

Removed validation within this PR #9390, now it supports any network