<!--

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**

DatabricksRunNowOperator is missing the option to take in key word arguement _jar_params_ , it already can take the other ones notebook_params,python_params,spark_submit_params. https://docs.databricks.com/dev-tools/api/latest/jobs.html#run-now


**Use case / motivation**

Provide parity with the other options

airflow/providers/databricks/operators/databricks.py
"""
    Submits a Spark job run to Databricks using the
    `api/2.0/jobs/runs/submit
    <https://docs.databricks.com/api/latest/jobs.html#runs-submit>`_
    API endpoint.
    There are two ways to instantiate this operator.
    In the first way, you can take the JSON payload that you typically use
    to call the ``api/2.0/jobs/runs/submit`` endpoint and pass it directly
    to our ``DatabricksSubmitRunOperator`` through the ``json`` parameter.
    For example ::
        json = {
          'new_cluster': {
            'spark_version': '2.1.0-db3-scala2.11',
            'num_workers': 2
          },
          'notebook_task': {
            'notebook_path': '/Users/airflow@example.com/PrepareData',