Currently `SlackWebhookHook` gets the token from `extra` but it would be more secure and intuitive to have it in password.

https://github.com/apache/airflow/blob/4fb5c017fe5ca41ed95547a857c9c39efc4f1476/airflow/providers/slack/hooks/slack_webhook.py
airflow/providers/slack/hooks/slack_webhook.py
self,
        http_conn_id=None,
        webhook_token=None,
        message="",
        attachments=None,
        blocks=None,
        channel=None,
        username=None,
        icon_emoji=None,
        icon_url=None,
        link_names=False,
        proxy=None,
        *args,
        **kwargs,
    ):
        super().__init__(http_conn_id=http_conn_id, *args, **kwargs)
        self.webhook_token = self._get_token(webhook_token, http_conn_id)
        self.message = message
        self.attachments = attachments
        self.blocks = blocks
        self.channel = channel
        self.username = username
        self.icon_emoji = icon_emoji
        self.icon_url = icon_url
        self.link_names = link_names
        self.proxy = proxy
    def _get_token(self, token: str, http_conn_id: Optional[str]) -> str: