**Description**
Let user specify the decode encoding used in WinRMOperator.

**Use case / motivation**

I'm trying to use winrm, but the task failed. After checked, I find https://github.com/apache/airflow/blob/master/airflow/providers/microsoft/winrm/operators/winrm.py#L117
```python
for line in stdout.decode('utf-8').splitlines():
    self.log.info(line)
for line in stderr.decode('utf-8').splitlines():
    self.log.warning(line)
```

But my remote host powershell's default encoding is  'gb2312'. I try https://stackoverflow.com/questions/40098771/changing-powershells-default-output-encoding-to-utf-8 's solution, i.e., put `PSDefaultParameterValues['Out-File:Encoding'] = 'utf8'` in `$PROFILE`. But it doesn't work in the WinRMOperator case.

The alternative way may be set the decode encoding in the operator to avoid error.


airflow/providers/microsoft/winrm/operators/winrm.py
self.winrm_hook = WinRMHook(ssh_conn_id=self.ssh_conn_id)
        if not self.winrm_hook:
            raise AirflowException("Cannot operate without winrm_hook or ssh_conn_id.")
        if self.remote_host is not None:
            self.winrm_hook.remote_host = self.remote_host
        if not self.command:
            raise AirflowException("No command specified so nothing to execute here.")
        winrm_client = self.winrm_hook.get_conn()
        
        try:
            self.log.info("Running command: '%s'...", self.command)
            command_id = self.winrm_hook.winrm_protocol.run_command(  
                winrm_client, self.command
            )
            
            stdout_buffer = []
            stderr_buffer = []
            command_done = False
            while not command_done:
                try:
                    
                    (
                        stdout,
                        stderr,
                        return_code,
                        command_done,
                    ) = self.winrm_hook.winrm_protocol._raw_get_command_output(  
                        winrm_client, command_id
                    )