**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
if self.do_xcom_push:
                        stdout_buffer.append(stdout)
                    stderr_buffer.append(stderr)
                    for line in stdout.decode('utf-8').splitlines():
                        self.log.info(line)
                    for line in stderr.decode('utf-8').splitlines():
                        self.log.warning(line)
                except WinRMOperationTimeoutError:
                    
                    
                    pass
            self.winrm_hook.winrm_protocol.cleanup_command(  
                winrm_client, command_id
            )
            self.winrm_hook.winrm_protocol.close_shell(winrm_client)  
        except Exception as e:
            raise AirflowException(f"WinRM operator error: {str(e)}")
        if return_code == 0:
            
            enable_pickling = conf.getboolean('core', 'enable_xcom_pickling')
            if enable_pickling:
                return stdout_buffer
            else:
                return b64encode(b''.join(stdout_buffer)).decode('utf-8')
        else:
            error_msg = "Error running cmd: {}, return code: {}, error: {}".format(
                self.command, return_code, b''.join(stderr_buffer).decode('utf-8')
            )
            raise AirflowException(error_msg)