vsphere-iso: Add support to set a VM storage policy while configuring hard disks

[ghost]

This issue was originally opened by @amitbhadra as hashicorp/packer#9525. It was migrated here as a result of the Packer plugin split. The original body of the issue is below.

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Feature Description

From the UI, we can select the VM Storage Policy when setting up the details of a Hard disk. This should be possible on Packer too.
Possibly something like -

"storage": [
        {
          "disk_size": 34816,
          "disk_controller_index": 0,
          "storage_policy": "<storage-policy-dev>"
        },
        {
          "disk_size": 51200,
          "disk_controller_index": 0,
          "storage_policy": "<storage-policy-prod>"
        }
],

Why do I have "disk_controller_index"? Because this is another use case already covered in hashicorp/packer#9518. I hope the new PR already has the changes from the previous issue I mentioned.

Use Case(s)

Based on whether the VM is dev or prod, the storage policy is changed.