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**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='redis_default',
            sql="SELECT count(1) FROM INFORMATION_SCHEMA.TABLES",
            dag=self.dag,
        )
        with pytest.raises(AirflowException):
            op.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, ignore_ti_state=True)
    @pytest.mark.backend("mysql")
    def test_sql_sensor_mysql(self):
        op1 = SqlSensor(
            task_id='sql_sensor_check_1',
            conn_id='mysql_default',
            sql="SELECT count(1) FROM INFORMATION_SCHEMA.TABLES",
            dag=self.dag,
        )
        op1.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, ignore_ti_state=True)
        op2 = SqlSensor(
            task_id='sql_sensor_check_2',
            conn_id='mysql_default',
            sql="SELECT count(%s) FROM INFORMATION_SCHEMA.TABLES",
            parameters=["table_name"],
            dag=self.dag,
        )
        op2.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, ignore_ti_state=True)
    @pytest.mark.backend("postgres")
    def test_sql_sensor_postgres(self):