"BIN file was corrupted, please download it again" should smartly resume and perhaps not reload entire game

[ell1e]

Thanks to the awesome #615 fix ❤️ I got to try to download a few multi part games again, but I ran into another curious corner case: I got a "BIN file was corrupted, please download it again" error for Fallout 3 GOTY. This seems a bit strange since even with an extremely shaky connection, TLS should usually ensure integrity. But assuming that this really was caused by a connection hiccup anyway, rather than some bug in the downloader, e.g. the downloader not transparently doing a HTTPS resume when the download fell short, there seem to be two things that are a bit odd about what happens after:

1. The message appearing in the first place. Usually, for a smart downloader e.g. like Steam, the established behavior would be to simply quietly resume redownloading the affected part. The user interaction doesn't really seem to be required here.

2. The way the recovery is done when redownloading. When I prompt it to restart, minigalaxy seems to then proceed to start over the entire game from scratch, rather than just the affected BIN file, at least from how the progress bar looks like. Especially for bigger games, which are now not uncommon on GOG, this seems like it doesn't really scale well if that's how errors are handled.

Affected minigalaxy version: 1.3.1 (via Flathub)