Take non-Clean URL requests into account

Can we get a test for this change.

The initial /index.php tests failed because the gitlab runner runs under a subdirectory whereas my local environment didn't.

It now takes the $base_path into account when making the test requests.

The test covers a lot more test cases, also opted to use a dedicated service for the stage_file_proxy http client rather than the generic one in case the behaviour needs to be altered for whatever reason e.g. for testing or custom implementation.

I don't think this issue has been fixed and probably needs further review.

The test-only CI pipeline fails to run because it requires the new stage_file_proxy.http_client service to decorate.

Can we clean up the pipeline

Actually upstream issue.

So what’s needed here exactly?