Consider adding `when` to `azapi_update_resource` resource

It would be great to be able to control when resources are updated (either during `apply` or `destroy`), like with `azapi_resource_action`. This would allow for scenarios such as reverting changes to resources. At the moment, i'm having to utilise `null_resource` with command provisioners to achieve this (horrible).

If there is appetite for adding this, I will raise a pull request to add this functionality