Add notifier for Smtp

[utkarsharma2]

Send email via SMTP notifier.

Example usage -

BashOperator(
            task_id="mytask",
            on_failure_callback=[
                send_smtp_notification(
                    mail_from="someone@mail.com",
                    to="someone@mail.com",
                    subject="[Error] The Task {{ ti.task_id }} failed",
                    html_content="debug logs",
                )
            ],
            bash_command="fail",
        )

[utkarsharma2]

The static checks failing are unrelated to this PR, please check the slack thread - https://apache-airflow.slack.com/archives/CCPRP7943/p1685011999082929

[ephraimbuddy]

We can import this from python directly now since 3.7 has been removed