Right now AWS Hooks obtain boto3.session.Session usual by call _get_credentials. This method return Tuple[boto3.session.Session, Optional[str]] and actually not return credentials, only session and endpoint_url.

Since #25336 all hook/connections configs stored in conn_config cached property, we do not need to call _get_credentials to obtain endpoint_url as well as other connection attributes.

Also change all aws hooks which uses this _get_credentials.

Right now (main branch) other providers do not use this method directly, however current version of PostgreSQL provider use this method (#25424), so we can't remove _get_credentials.

Some minor changes - remove information about that S3 Bucket has not region (#20463). In fact AWS S3 Buckets has region in other hand you could access to any buckets from any region if you have a permission (might be only one limitation endpoint should be in the same AWS Region Partition).

cc: @vincbeck @ferruzzi @o-nikolas @potiuk