Missing module for managing router nats

##### SUMMARY
I would like to request a module for manipulating router nat configuration.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
google.cloud. gcp_compute_router_nats

##### ADDITIONAL INFORMATION
The equivalent gcloud command is `gcloud compute routers nats` and the rationale for this is that I am using the google.cloud module to configure private GKE clusters which need a NAT router for external access.

Start with the `gcloud compute routers nats` command and the `google.cloud.gcp_compute_router_nats` component context to determine the module's required operations and scope. Done means the google.cloud collection can manipulate router NAT configuration for the stated private GKE use case.

Written by the indexing model from the issue text.