Avoid circular imports in AWS Secrets Backends if obtain secrets from config

[Taragolis]

PR #25628 add new possibility with circular imports in Secrets Backends.
It affect both AWS secrets backends in case if user want to retrieve secrets configs from SB.

How to reproduce

❯ export AIRFLOW__SECRETS__BACKEND=airflow.providers.amazon.aws.secrets.systems_manager.SystemsManagerParameterStoreBackend
❯ export AIRFLOW__SECRETS__BACKEND_KWARGS='{"config_prefix": "/airflow/config", "region_name": "eu-west-1"}'
❯ export AIRFLOW__DATABASE__SQL_ALCHEMY_CONN_SECRET=boom
❯ airflow config get-value database sql_alchemy_conn

...

airflow.exceptions.AirflowConfigException: Cannot retrieve config from alternative secrets backend. Make sure it is configured properly and that the Backend is accessible.
Cannot retrieve config from alternative secrets backend. Make sure it is configured properly and that the Backend is accessible.
cannot import name 'SessionFactory' from partially initialized module 'airflow.providers.amazon.aws.hooks.base_aws' (most likely due to a circular import) (/Users/taragolis/Projects/common/airflow/airflow/providers/amazon/aws/hooks/base_aws.py)

After this changes

❯ export AIRFLOW__SECRETS__BACKEND=airflow.providers.amazon.aws.secrets.systems_manager.SystemsManagerParameterStoreBackend
❯ export AIRFLOW__SECRETS__BACKEND_KWARGS='{"config_prefix": "/airflow/config", "region_name": "eu-west-1"}'
❯ export AIRFLOW__DATABASE__SQL_ALCHEMY_CONN_SECRET=boom
❯ airflow config get-value database sql_alchemy_conn

[2022-09-29 22:27:59,204] {credentials.py:1180} INFO - Found credentials in environment variables.
[2022-09-29 22:27:59,665] {credentials.py:1180} INFO - Found credentials in environment variables.
sqlite:////Users/taragolis/airflow/airflow-from-ssm.db

closes: #26754

[vincbeck]

LGTM

[uranusjr]

I think we should consolidate these types a bit, perhaps with a Protocol.

[Taragolis]

Yeah, I agree with you. Main problem with this class that when I initially create this helper I added InitVar and add some limitation with define attributes for this class. I have a plan to refactor it later and also get rid of _ConnectionMetadata.