<!--

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**

A sql sensor which uses Standard SQL due to default one uses legacy sql


**Use case / motivation**

Currently (correct me if I am wrong!), the sql sensor only supports legacy sql. If I want to poke a BQ table, I do not think I can do that using standard sql right now.


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

If community approves of this idea, sure!


tests/sensors/test_sql_sensor.py
op = SqlSensor(
            task_id='sql_sensor_check', conn_id='postgres_default', sql="SELECT 1", fail_on_empty=True
        )
        mock_hook.get_connection('postgres_default').conn_type = "postgres"
        mock_get_records = mock_hook.get_connection.return_value.get_hook.return_value.get_records
        mock_get_records.return_value = []
        with pytest.raises(AirflowException):
            op.poke(None)
    @mock.patch('airflow.sensors.sql.BaseHook')
    def test_sql_sensor_postgres_poke_success(self, mock_hook):
        op = SqlSensor(
            task_id='sql_sensor_check', conn_id='postgres_default', sql="SELECT 1", success=lambda x: x in [1]
        )
        mock_hook.get_connection('postgres_default').conn_type = "postgres"
        mock_get_records = mock_hook.get_connection.return_value.get_hook.return_value.get_records
        mock_get_records.return_value = []
        assert not op.poke(None)
        mock_get_records.return_value = [[1]]
        assert op.poke(None)
        mock_get_records.return_value = [['1']]
        assert not op.poke(None)
    @mock.patch('airflow.sensors.sql.BaseHook')
    def test_sql_sensor_postgres_poke_failure(self, mock_hook):