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.
Before, it was shown by UI when the chat is empty, however, in case of
verified groups, this is never the case any longer as the 'e2ee now
guaranteed' is always added.
It can be used e.g. as a default in the file saving dialog. Also display the original filename in
the message info. For these purposes add Param::Filename in addition to Param::File and use it as an
attachment filename in sent emails.
