**Description**

`BigQueryInsertJobOperator` requires the submission of a `configuration` parameter in the form of a dict.  Unfortunately, if this contains a large SQL query - especially one that is formatted with new lines - then this cannot currently be rendered very nicely in the UI.

<img width="1670" alt="Screenshot 2021-07-15 at 15 39 33" src="https://user-images.githubusercontent.com/967119/125806943-839d57a9-d4a0-492d-b130-06432b095239.png">

**Use case / motivation**

The issue with this is that it's impossible to copy and paste the rendered query out of the Airflow UI, into a BigQuery browser and run it without lots of manual edits which is time wasted when troubleshooting problems.

**Are you willing to submit a PR?**

Yes.  My current thought process around this would be to add an optional SQL parameter to the operator which, if provided, would be added into the configuration and could therefore have its own template field and SQL renderer.

e.g.

<img width="1570" alt="Screenshot 2021-07-14 at 14 18 09" src="https://user-images.githubusercontent.com/967119/125808200-5f30b8f4-4def-48a7-8223-82afdc65c973.png">


airflow/providers/google/cloud/operators/bigquery.py
gcp_conn_id = bigquery_conn_id
        warnings.warn(
            "This operator is deprecated. Please use `BigQueryInsertJobOperator`.",
            DeprecationWarning,
            stacklevel=2,
        )
        self.sql = sql
        self.destination_dataset_table = destination_dataset_table
        self.write_disposition = write_disposition
        self.create_disposition = create_disposition
        self.allow_large_results = allow_large_results
        self.flatten_results = flatten_results
        self.gcp_conn_id = gcp_conn_id
        self.delegate_to = delegate_to
        self.udf_config = udf_config
        self.use_legacy_sql = use_legacy_sql
        self.maximum_billing_tier = maximum_billing_tier
        self.maximum_bytes_billed = maximum_bytes_billed
        self.schema_update_options = schema_update_options
        self.query_params = query_params
        self.labels = labels
        self.priority = priority
        self.time_partitioning = time_partitioning
        self.api_resource_configs = api_resource_configs
        self.cluster_fields = cluster_fields
        self.location = location
        self.encryption_configuration = encryption_configuration
        self.hook = None  
        self.impersonation_chain = impersonation_chain
    def execute(self, context):