### Apache Airflow version

main (development)

### What happened

Here's a dag:

```python3
from airflow import DAG
from airflow.decorators import task
import airflow.configuration as conf
from datetime import datetime

@task
def print_this(this):
    print(this)

with DAG(dag_id="config_ref", schedule=None, start_date=datetime(1970, 1, 1)) as dag:
    namespace = conf.get("kubernetes", "NAMESPACE")
    print_this(namespace)
```

In 2.4.3 it parses without error, but in main (as of 2e7a4bcb550538283f28550208b01515d348fb51) the reference to the "kubernetes" section breaks.  Likely because of this: https://github.com/apache/airflow/pull/26873
```
❯ airflow dags list-import-errors
filepath                              | error
======================================+========================================================================================================
/Users/matt/2022/11/29/dags/config.py | Traceback (most recent call last):
                                      |   File "/Users/matt/src/airflow/airflow/configuration.py", line 595, in get
                                      |     return self._get_option_from_default_config(section, key, **kwargs)
                                      |   File "/Users/matt/src/airflow/airflow/configuration.py", line 605, in _get_option_from_default_config
                                      |     raise AirflowConfigException(f"section/key [{section}/{key}] not found in config")
                                      | airflow.exceptions.AirflowConfigException: section/key  not found in config
                                      |

❯ python dags/config.py
[2022-11-29 21:30:05,300] {configuration.py:603} WARNING - section/key [kubernetes/namespace] not found in config
Traceback (most recent call last):
  File "/Users/matt/2022/11/29/dags/config.py", line 13, in <module>
    namespace = conf.get("kubernetes", "NAMESPACE")
  File "/Users/matt/src/airflow/airflow/configuration.py", line 1465, in get
    return conf.get(*args, **kwargs)
  File "/Users/matt/src/airflow/airflow/configuration.py", line 595, in get
    return self._get_option_from_default_config(section, key, **kwargs)
  File "/Users/matt/src/airflow/airflow/configuration.py", line 605, in _get_option_from_default_config
    raise AirflowConfigException(f"section/key [{section}/{key}] not found in config")
airflow.exceptions.AirflowConfigException: section/key [kubernetes/namespace] not found in config
```

To quote @jedcunningham :
>  The backcompat layer only expects you to use the “new” section name.




### What you think should happen instead

The recent section name change should be registered so that the old name still works.

### How to reproduce

See above

### Operating System

Mac OS / venv

### Versions of Apache Airflow Providers

n/a

### Deployment

Virtualenv installation

### Deployment details

`pip install -e ~/src/airflow` into a fresh venv

### Anything else

Also, it's kind of weird that the important part of the error message (which section?) is missing from `list-import-errors`.  I had to run the dag def like a script to realize that it was the kubernetes section that it was complaining about.


### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

("logging", "log_filename_template"): ("core", "log_filename_template", "2.0.0"),
        ("logging", "log_processor_filename_template"): ("core", "log_processor_filename_template", "2.0.0"),
        ("logging", "dag_processor_manager_log_location"): (
            "core",
            "dag_processor_manager_log_location",
            "2.0.0",
        ),
        ("logging", "task_log_reader"): ("core", "task_log_reader", "2.0.0"),
        ("metrics", "statsd_on"): ("scheduler", "statsd_on", "2.0.0"),
        ("metrics", "statsd_host"): ("scheduler", "statsd_host", "2.0.0"),
        ("metrics", "statsd_port"): ("scheduler", "statsd_port", "2.0.0"),
        ("metrics", "statsd_prefix"): ("scheduler", "statsd_prefix", "2.0.0"),
        ("metrics", "statsd_allow_list"): ("scheduler", "statsd_allow_list", "2.0.0"),
        ("metrics", "stat_name_handler"): ("scheduler", "stat_name_handler", "2.0.0"),
        ("metrics", "statsd_datadog_enabled"): ("scheduler", "statsd_datadog_enabled", "2.0.0"),
        ("metrics", "statsd_datadog_tags"): ("scheduler", "statsd_datadog_tags", "2.0.0"),
        ("metrics", "statsd_custom_client_path"): ("scheduler", "statsd_custom_client_path", "2.0.0"),
        ("scheduler", "parsing_processes"): ("scheduler", "max_threads", "1.10.14"),
        ("scheduler", "scheduler_idle_sleep_time"): ("scheduler", "processor_poll_interval", "2.2.0"),
        ("operators", "default_queue"): ("celery", "default_queue", "2.1.0"),
        ("core", "hide_sensitive_var_conn_fields"): ("admin", "hide_sensitive_variable_fields", "2.1.0"),
        ("core", "sensitive_var_conn_names"): ("admin", "sensitive_variable_fields", "2.1.0"),
        ("core", "default_pool_task_slot_count"): ("core", "non_pooled_task_slot_count", "1.10.4"),
        ("core", "max_active_tasks_per_dag"): ("core", "dag_concurrency", "2.2.0"),
        ("logging", "worker_log_server_port"): ("celery", "worker_log_server_port", "2.2.0"),
        ("api", "access_control_allow_origins"): ("api", "access_control_allow_origin", "2.2.0"),
        ("api", "auth_backends"): ("api", "auth_backend", "2.3.0"),
        ("database", "sql_alchemy_conn"): ("core", "sql_alchemy_conn", "2.3.0"),
        ("database", "sql_engine_encoding"): ("core", "sql_engine_encoding", "2.3.0"),
        ("database", "sql_engine_collation_for_ids"): ("core", "sql_engine_collation_for_ids", "2.3.0"),