Is your feature request related to a problem? Please describe.
Currently, govmomi doesn't support all the appliance management APIs. We need to support most of these API's

Describe the solution you'd like
As a first step to support most of the appliance mgmt API, we need to add Appliance Shutdown APIs.
We can take this as a reference, to add the API's
https://developer.vmware.com/apis/vsphere-automation/latest/appliance/appliance/shutdown/