Retry shelving a file if the file size on /stacks doesn't match the original file

[andrewjbtw]

(This issue comes out of discussion on #5187)

If a file is being shelved and the process fails before the file has been copied fully to Stacks, retry shelving that file. Currently, if the shelving operation is cut off in progress, the copy of the file on Stacks is truncated. This results in Stacks serving a broken file via embed.

Suggestion from @justinlittman in Slack:

One possible approach to preventing this is to have https://github.com/sul-dlss/purl-fetcher/blob/main/app/services/files_by_md5_service.rb also check the file size. Currently, it omits a file if the file doesn't exist on disk; it could also omit if the file's size didn't match. This would cause check_stacks to fail when publishing (https://github.com/sul-dlss/dor-services-app/blob/main/app/services/publish/metadata_transfer_service.rb#L27) and would cause the file to be recopied when retrying.