Autopilot

##### SUMMARY

Support autopilot clusters

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME

Google Kubernetes Engine Cluster

##### ADDITIONAL INFORMATION

Allow creation of an autopilot GKE cluster

```yaml
- name: create a cluster
google.cloud.gcp_container_cluster:
name: my-cluster
initial_node_count: 2
master_auth:
username: cluster_admin
password: my-secret-password
autopilot: true
location: us-central1-a
project: test_project
auth_kind: serviceaccount
service_account_file: "/tmp/auth.pem"
state: present
```

Start at the google.cloud.gcp_container_cluster module entry point and review how the existing cluster options map to GKE. Use the provided YAML as the target usage, then verify that an autopilot cluster can be created with the requested location, project, authentication, and state settings.

Written by the indexing model from the issue text.