Exports are not sufficient for configuring some object stores, for example minio running locally

[winding-lines]

Describe the bug
When running minio locally for testing the default setup is to use http. The object_store crate supports this setup, however one of the required symbols is not exported.

To Reproduce

In order to connect with minio over http you'd use code similar to the following

use object_store::AmazonS3ConfigKey as Key;
use object_store::ClientConfigKey; // <- export missing
use object_store::aws::AmazonS3Builder;

def foo() {
        
  let out builder = AmazonS3Builder().new();
  builder = builder.with_config(Key::AccessKeyId, &cred.access_key.unwrap());
  builder = builder.with_config(Key::SecretAccessKey, &cred.secret_key.unwrap());
  builder = builder.with_config(Key::Client(ClientConfigKey::AllowHttp), &"true".into());
  builder = builder.with_config(Key::Endpoint, &"http://localhost:9000".into()));
}

Expected behavior
The code should compile, but it does not because of the private ClientConfigKey.

Additional context

[winding-lines]

Looks like this was already fixed as part of #4515

[tustvold]

label_issue.py automatically added labels {'object-store'} from #4531