az network nat gateway

### **This is autogenerated. Please review and update as needed.**

## Describe the bug

**Command Name**
`az network nat gateway create`

**Errors:**
```
'NatGatewaysOperations' object has no attribute 'begin_create_or_update'
Traceback (most recent call last):
python3.6/dist-packages/knack/cli.py, ln 215, in invoke
cmd_result = self.invocation.execute(args)
cli/core/commands/__init__.py, ln 654, in execute
raise ex
cli/core/commands/__init__.py, ln 718, in _run_jobs_serially
results.append(self._run_job(expanded_arg, cmd_copy))
...
azure/cli/core/__init__.py, ln 782, in default_command_handler
return op(**command_args)
cli/command_modules/natgateway/custom.py, ln 34, in create_nat_gateway
return sdk_no_wait(no_wait, client.begin_create_or_update, resource_group_name, nat_gateway_name, nat_gateway)
AttributeError: 'NatGatewaysOperations' object has no attribute 'begin_create_or_update'
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- _Put any pre-requisite steps here..._
- `az network nat gateway create --resource-group {} --name {} --public-ip-addresses {} --idle-timeout {}`

## Expected Behavior

## Environment Summary
```
Linux-5.4.0-1048-azure-x86_64-with-Ubuntu-18.04-bionic
Python 3.6.9
Installer: PIP

azure-cli 2.11.1

```
## Additional Context