Provision / delete Greengrass V2 cores.

If type is Create, a task is created to provision 1 or more Greengrass V2 cores based on a predefined provisioning templates. If type is Delete then the task created is to delete 1 or more cores. When Create, if the referenced thingName does not exist, an AWS IoT Thing is provisioned using the provided provisioningTemplate, then configured as a Greengrass V2 Core device. If it exists, the AWS IoT Thing is not updated but the Greengrass V2 Core device configuration is. This is an asynchronous call, meaning that when submitted the call will return immediately with a taskId while the cores are being created/deleted in the background. Use the GET /coreTasks/{taskId} to retrieve the status of the task.