<!--

Welcome to Apache Airflow!  For a smooth issue process, try to answer the following questions.
Don't worry if they're not all applicable; just try to include what you can :-)

If you need to include code snippets or logs, please put them in fenced code
blocks.  If they're super-long, please use the details tag like
<details><summary>super-long log</summary> lots of stuff </details>

Please delete these comment blocks before submitting the issue.

-->

**Description**

Related to the discussion here: https://github.com/apache/airflow/pull/8553#discussion_r416136954

Allow user to define expected terminal state. e.g. `JOB_STATE_CANCELLED` could be not treated as failure but expected terminal state.


<!-- A short description of your feature -->


You cannot call ``PipelineResult.wait_until_finish`` method in your pipeline code for the operator
            to work properly. i. e. you must use asynchronous execution. Otherwise, your pipeline will
            always wait until finished. For more information, look at:
            `Asynchronous execution
            <https://cloud.google.com/dataflow/docs/guides/specifying-exec-params#python_10>`__
        The process of starting the Dataflow job in Airflow consists of two steps:
        * running a subprocess and reading the stderr/stderr log for the job id.
        * loop waiting for the end of the job ID from the previous step.
          This loop checks the status of the job.
        Step two is started just after step one has finished, so if you have wait_until_finished in your
        pipeline code, step two will not start until the process stops. When this process stops,
        steps two will run, but it will only execute one iteration as the job will be in a terminal state.
        If you in your pipeline do not call the wait_for_pipeline method but pass wait_until_finish=True
        to the operator, the second loop will wait for the job's terminal state.
        If you in your pipeline do not call the wait_for_pipeline method, and pass wait_until_finish=False
        to the operator, the second loop will check once is job not in terminal state and exit the loop.
    :param impersonation_chain: Optional service account to impersonate using short-term
        credentials, or chained list of accounts required to get the access_token
        of the last account in the list, which will be impersonated in the request.
        If set as a string, the account must grant the originating account
        the Service Account Token Creator IAM role.
        If set as a sequence, the identities from the list must grant
        Service Account Token Creator IAM role to the directly preceding identity, with first
        account from the list granting this role to the originating account (templated).
    :param deferrable: Run operator in the deferrable mode.
    :param append_job_name: True if unique suffix has to be appended to job name.
    """
    template_fields: Sequence[str] = ("body", "location", "project_id", "gcp_conn_id")
    operator_extra_links = (DataflowJobLink(),)
    def __init__(