remove msys/cygwin support, bugfixes, and cleanup

remove msys/cygwin support, bugfixes, and cleanup

zshenv:
- check for and fix broken TERM
- reset path to home for login shells, for convenience
zprofile:
- fixed agent setup
- tmp folders are now handled better and do not use XDG_CACHE_HOME as root
- remove all msys/cywgin compat
zlogout:
- safer cleanup of paths
- don't clear if not interactive
prompt_arrows_setup:
- fixed color detection