use Equinix Metal VMWare vSphere module

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Use the equinix/vsphere/metal module

• Removes duplication of vsphere provisioning functionality from this
  module
• Requires updating the module to TF 0.13
• Requires upgrading the Packet provider to Equinix Metal
• Adds new input variables required by the vsphere module
• Adds descriptions to outputs whose values previously included a
  description (making the value field concise and reusable)

Fixes #113
Part of #122
Part of #91

Relies heavily on the changes @c0dyhi11 made to the vSphere module in equinix/terraform-metal-vsphere#7 💪

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I should add description to any variable that doesn't have one. This is mostly copy/paste from the vsphere module which added descriptions.

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Two provisioning errors on the first pass, both confined to the vsphere module:

module.vsphere.null_resource.run_pre_reqs (remote-exec): mkdir: cannot create directory ‘/root/bootstrap/’: File exists
module.vsphere.null_resource.download_vcenter_iso (remote-exec): bash: /root/bootstrap/download_vcenter.sh: Not a directory

I ran into the same problem when adding integration tests to that module:
equinix/terraform-metal-vsphere#13

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I've been running into some more full e2e test failures on the vsphere module, tracking that here:
equinix/terraform-metal-vsphere#19

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I'm missing GCP keys for the added integration test.