Create S3 repository tests that test against a real S3 bucket

[abeyad]

Right now, the repository-s3 plugin relies on tests that mocks the AmazonS3 client. However, this is a limited form of testing that does not bring to light issues one would find when interacting with the real Amazon SDK connecting to a real S3 repository. Such tests are essential in uncovering even basic issues of interaction between our integration and the Amazon SDK. As an example, see #20861 which would have been uncovered with such tests.

[tlrx]

This issue is still a valid issue. We plan to create better integration tests for repository plugins using fixtures (we started the work with Google Cloud Storage in #28788) that will help to catch more bugs.

Once those tests are available, we'd like to be able to run them against a local fixture or against the real service.

[tlrx]

Closed by #29372