Fix parsing issues with 'ghcup run' and non-PVP versions
This is a major refactor of some CLI code. We try to distinguish GHC versions from other versions, so that we can use distinct parsers.
Hopefully this doesn't introduce new bugs.
This also forces ghcup run
to use the new internal ~/.ghcup/tmp
dir. This should fix #329 (comment 441695)
Edited by Julian Ospald