Make ghc installation consistent across all os's (use ghcup as fallback for windows)

[jneira]

• Somewhat follow up of Consider ghcup for windows #70
• Afaik linux is using apt-get as the first method to install ghc and fallback to ghcup. However, as hvr/ppa is not updated anymore it is using ghcup for ghc >= 8.10
• Windows only uses chocolatey without fallback so sometimes you can install a new ghc version in linux cause it is in ghcup but no in windows cause it still was not uploaded (see Consider ghcup for windows #70 (comment))
• Otoh sometimes (more frequently than we want) the ghc release is broken in windows. The choco package maitainer try to fix the release downstream so use it to get a working ghc version would be good.
• Quoting @jared-w in the mentioned issue:

I think the windows images from GitHub still use chocolatey under the hood, so I would still default to that (for fastest setup time in the cloud), but I'm looking forward to being able to fall back to ghcup on Windows and possibly even switch to using it first if the action images start using ghcup for windows too.