Add a notification when failing to load .7z/.zip

[bslenul]

Currently when you try to load a game from a .7z/.zip archive the core closes with a generic "Failed to load content" and can even crash RetroArch depending on the video driver. In any case nothing is printed in logs, so the user has absolutely no idea why it's failing/crashing.

With this PR the user gets a notification (which is also printed in logs) to warn them that the core doesn't support compressed content:

https://github.com/libretro/dolphin/assets/33353403/0fa651df-c67c-401f-a238-7f00db1cc451

And the core should not crash (because it will return false BEFORE the Libretro::Video::Init() call, which seems to be the culprit for the crashes).

Anyway I hope this is OK, the goal is really just to give the user a reason for why it's failing, idk if there's a better way of doing it.