This way filenames in the blobstorage are just random hex numbers. This also allows us to get rid of
the `sanitize-filename` dependency.
This also requires `Param::Filename` to be set to "debug_logging*.xdc" for messages containing
logging webxdc-s, otherwise they are not detected properly. This is done in "fix:
Message::set_file_from_bytes(): Set Param::Filename", so don't forget to update senders as well.
