1. MediaTransformOutput::streamFile() and FileRepo::streamFile() should not convert the Status object to boolean when returning success/failure
2. callers to these functions (at least thumb.php, img_auth.php, SpecialUndelete#showFile, SpecialRevisiondelete#tryShowFile and SpecialUploadStash#outputLocalFile) should look at the return value and raise a proper error if the streaming failed.

(Split from T92545.)