Improve logging in bob.extension.download.get_file

Even when set verbosity level to 2 (-vv), there is no information that networks are downloaded. Hence, when running a pipeline for the first time, there is no response on the console for a couple of minutes (I can only see the Ethernet usage to increase).

I would suggest to add a logging info message when downloading, e.g., here: https://gitlab.idiap.ch/bob/bob.bio.face/-/blob/e8e95bf04a73f8e60ba5a997392afb4e6c4a64fd/bob/bio/face/embeddings/opencv.py#L117

The question is if we should do that here or if we should add an info message inside the bob.extension.download.get_file method directly.