**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: Optional[WinRMHook] = None,
        ssh_conn_id: Optional[str] = None,
        remote_host: Optional[str] = None,
        command: Optional[str] = None,
        timeout: int = 10,
        **kwargs,
    ) -> None:
        super().__init__(**kwargs)
        self.winrm_hook = winrm_hook
        self.ssh_conn_id = ssh_conn_id
        self.remote_host = remote_host
        self.command = command
        self.timeout = timeout
    def execute(self, context: dict) -> Union[list, str]:
        if self.ssh_conn_id and not self.winrm_hook:
            self.log.info("Hook not found, creating...")