gac: `deployments/configurator.nix` has AWS-specific code in it

[kaii-zen]

This file is used by all GAC-based deployments for the purpose of sharing configuration parameters between NixOS VMs/instances and the Nixops configs that deploy them. It also contains some definitions of AWS resources. While the configuration-parameter management aspect of it is needed by all GAC deployments, the AWS resources are only needed by deployments to AWS instances. We therefore need to be able to include those parts separately.