**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
#
#
#
import logging
from base64 import b64encode
from typing import Optional, Union
from winrm.exceptions import WinRMOperationTimeoutError
from airflow.configuration import conf
from airflow.exceptions import AirflowException
from airflow.models import BaseOperator
from airflow.providers.microsoft.winrm.hooks.winrm import WinRMHook
from airflow.utils.decorators import apply_defaults
logging.getLogger('urllib3.connectionpool').setLevel(logging.ERROR)
class WinRMOperator(BaseOperator):
    """
    WinRMOperator to execute commands on given remote host using the winrm_hook.
    :param winrm_hook: predefined ssh_hook to use for remote execution
    :type winrm_hook: airflow.providers.microsoft.winrm.hooks.winrm.WinRMHook
    :param ssh_conn_id: connection id from airflow Connections
    :type ssh_conn_id: str
    :param remote_host: remote host to connect
    :type remote_host: str
    :param command: command to execute on remote host. (templated)
    :type command: str
    :param timeout: timeout for executing the command.
    :type timeout: int
    """
    template_fields = ('command',)
    @apply_defaults
    def __init__(