[Feature Request] Support remote config dependencies with v2 Cloud Build repositories

[mattsanta]

Currently remote config dependencies supports Skaffold configs stored in a git repository and Google Cloud Storage. Unfortunately, the git repository option requires the credentials to already be set up in the local workspace in order to access private git repositories.

As an alternative it would be nice if a user could configure a Cloud Build v2 repository where the Skaffold config is stored and Skaffold handles setting up the credentials using CB repositories accessReadToken and then pulls the repository to resolve the config dependencies.