### Overview
Some Executors, currently a subset of the local Executors, run in a single threaded fashion and have certain limitations and requirements, many of which are hardcoded. To add a new single threaded Executor would require changes to core Airflow code.
Note: This coupling often shows up with SQLite compatibility checks since it does not support multiple connections.
### Examples
- **2a**) SQLite check done in configuration.py: https://github.com/apache/airflow/blob/26f94c5370587f73ebd935cecf208c6a36bdf9b6/airflow/configuration.py#L412-L419
- **2b**) When running in standalone mode SQLite compatibility is checked: https://github.com/apache/airflow/blob/26f94c5370587f73ebd935cecf208c6a36bdf9b6/airflow/cli/commands/standalone_command.py#L160-L165
- **2c**) Sensors in `poke` mode can block execution of DAGs when running with single process Executors, currently hardcoded to DebugExecutor (although should also include SequentialExecutor): https://github.com/apache/airflow/blob/27e2101f6ee5567b2843cbccf1dca0b0e7c96186/airflow/sensors/base.py#L243
### Proposal
A static method or attribute on the Executor class which can be checked by core code.

There is a precedent already set with the `supports_ad_hoc_ti_run` attribute, see:
https://github.com/apache/airflow/blob/fb741fd87254e235f99d7d67e558dafad601f253/airflow/executors/kubernetes_executor.py#L435 https://github.com/apache/airflow/blob/26f94c5370587f73ebd935cecf208c6a36bdf9b6/airflow/www/views.py#L1735-L1737
negative_timeout = -25
        non_number_timeout = "abcd"
        positive_timeout = 25
        with pytest.raises(AirflowException):
            DummySensor(
                task_id="test_sensor_task_1", return_value=None, poke_interval=10, timeout=negative_timeout
            )
        with pytest.raises(AirflowException):
            DummySensor(
                task_id="test_sensor_task_2", return_value=None, poke_interval=10, timeout=non_number_timeout
            )
        DummySensor(
            task_id="test_sensor_task_3", return_value=None, poke_interval=10, timeout=positive_timeout
        )
    def test_sensor_with_exponential_backoff_off(self):
        sensor = DummySensor(
            task_id=SENSOR_OP, return_value=None, poke_interval=5, timeout=60, exponential_backoff=False
        )
        started_at = timezone.utcnow() - timedelta(seconds=10)
        def run_duration():
            return (timezone.utcnow - started_at).total_seconds()
        assert sensor._get_next_poke_interval(started_at, run_duration, 1) == sensor.poke_interval
        assert sensor._get_next_poke_interval(started_at, run_duration, 2) == sensor.poke_interval
    def test_sensor_with_exponential_backoff_on(self):