On Google Container Platform can Kubernetes nodes (or node pools) be configured to have multiple network interfaces?
Unfortunately they cannot. All of the parameters that you can configure through the Google Kubernetes Engine API are here.
If you want to customize the nodes beyond what is offered through the API you can create your own instance template as described in this stackoverflow answer. The downside is that you will no longer be able to manage the nodes via the Google Kubernetes Engine API (e.g. for upgrading).