Improve GOG detection by logging the results

[Pickysaurus]

Unlike the Steam detection (which uses a Logger), the GOG detection uses new ErrorMessage(), which, when used in the Nexus Mods app, does not appear to beprinted anywhere.

As we're having problems with GOG detecting DLCs, we should improve this logging. Perhaps reporting when Galaxy is found, and then which registry keys are valid.

[halgari]

Looking at the code, it's strange, because we do log these messages. Is there a specific failure case we can replicate to test this?

[Pickysaurus]

When it fails to identify the cyberpunk DLCs in the app, there are no logs from Game finder related to GOG