[request] Add support for SEV provisioning in Azure

[zizhong]

Please describe problem to be solved
Currently Skyplane doesn't support provision confidential VMs in Azure.

⠏ Provisioning VMs ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 0/1 0:00:2921:05:49 [ERROR] Error running _provision_task: (BadRequest) The VM size 'Standard_DC2as_v5' is not supported for creation of VMs and Virtual
Machine Scale Set with '<NULL>' security type.
Code: BadRequest
Message: The VM size 'Standard_DC2as_v5' is not supported for creation of VMs and Virtual Machine Scale Set with '<NULL>' security type.
Traceback (most recent call last):
  File "/home/zzz/workspace/skyplane/skyplane/cli/cli_transfer.py", line 353, in cp
    dp.provision(spinner=True)
  File "/home/zzz/workspace/skyplane/skyplane/api/dataplane.py", line 126, in provision
    uuids = self.provisioner.provision(
  File "/home/zzz/workspace/skyplane/skyplane/api/provisioner.py", line 205, in provision
    results: List[Tuple[ProvisionerTask, compute.Server]] = do_parallel(
  File "/home/zzz/workspace/skyplane/skyplane/utils/fn.py", line 57, in do_parallel
    args, result = future.result()
  File "/home/zzz/.pyenv/versions/3.8.10/lib/python3.8/concurrent/futures/_base.py", line 437, in result
    return self.__get_result()
  File "/home/zzz/.pyenv/versions/3.8.10/lib/python3.8/concurrent/futures/_base.py", line 389, in __get_result
    raise self._exception
  File "/home/zzz/.pyenv/versions/3.8.10/lib/python3.8/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/zzz/workspace/skyplane/skyplane/utils/fn.py", line 43, in wrapped_fn
    return args, func(args)
  File "/home/zzz/workspace/skyplane/skyplane/api/provisioner.py", line 154, in _provision_task
    server = self.azure.provision_instance(task.region, task.vm_type, use_spot_instances=task.spot, tags=task.tags)
  File "/home/zzz/workspace/skyplane/skyplane/utils/imports.py", line 33, in wrapped
    return fn(*modules_imported, *args, **kwargs)
  File "/home/zzz/workspace/skyplane/skyplane/compute/azure/azure_cloud_provider.py", line 342, in provision_instance
    poller = compute_client.virtual_machines.begin_create_or_update(
  File "/home/zzz/.pyenv/versions/3.8.10/envs/skyplane/lib/python3.8/site-packages/azure/core/tracing/decorator.py", line 78, in
wrapper_use_tracer
    return func(*args, **kwargs)
  File
"/home/zzz/.pyenv/versions/3.8.10/envs/skyplane/lib/python3.8/site-packages/azure/mgmt/compute/v2022_11_01/operations/_virtual_machines_operation
s.py", line 1358, in begin_create_or_update
    raw_result = self._create_or_update_initial(
  File
"/home/zzz/.pyenv/versions/3.8.10/envs/skyplane/lib/python3.8/site-packages/azure/mgmt/compute/v2022_11_01/operations/_virtual_machines_operation
s.py", line 1229, in _create_or_update_initial
    raise HttpResponseError(response=response, error_format=ARMErrorFormat)
azure.core.exceptions.HttpResponseError: (BadRequest) The VM size 'Standard_DC2as_v5' is not supported for creation of VMs and Virtual Machine
Scale Set with '<NULL>' security type.
Code: BadRequest
Message: The VM size 'Standard_DC2as_v5' is not supported for creation of VMs and Virtual Machine Scale Set with '<NULL>' security type.

(Optional): Suggest a solution
Rework on the provisioning code to support the creation of CVM

• Details of the technical implementation
  If the vm instance is CVM, we need to set the security profile and the os profile to a proper value.
• Tradeoffs made in design decisions
• Caveats and considerations for the future)
  TODO add CVM provisioning for other cloud providers as well.