### 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
sensor = DummySensor(
            task_id=SENSOR_OP, return_value=None, poke_interval=5, timeout=60, exponential_backoff=True
        )
        with patch("airflow.utils.timezone.utcnow") as mock_utctime:
            mock_utctime.return_value = DEFAULT_DATE
            started_at = timezone.utcnow() - timedelta(seconds=10)
            def run_duration():
                return (timezone.utcnow - started_at).total_seconds()
            interval1 = sensor._get_next_poke_interval(started_at, run_duration, 1)
            interval2 = sensor._get_next_poke_interval(started_at, run_duration, 2)
            assert interval1 >= 0
            assert interval1 <= sensor.poke_interval
            assert interval2 >= sensor.poke_interval
            assert interval2 > interval1
    def test_sensor_with_exponential_backoff_on_and_max_wait(self):
        sensor = DummySensor(
            task_id=SENSOR_OP,
            return_value=None,
            poke_interval=10,
            timeout=60,
            exponential_backoff=True,
            max_wait=timedelta(seconds=30),
        )
        with patch("airflow.utils.timezone.utcnow") as mock_utctime:
            mock_utctime.return_value = DEFAULT_DATE
            started_at = timezone.utcnow() - timedelta(seconds=10)
            def run_duration():