ghc installation is way too verbose

When running ghcup install it writes everything to the console that its doing in the background (several hundred lines) which I don't need to see unless something goes wrong.

If we were to hide it by default and dump it into a log file (maybe ~/.ghcup/.log or something like that) then only important information is surfaced to the user and they're less likely to miss something important (like needing to update their PATH).