Fixes for test installers

[edslocomb]

Fix various installers, to get a clean make fmt-build

1. Backports from #200
   • Use new universal installer for Nodejs
   • install prettier-ruby and prettier-svelte plugins locally in /tmp
   • use newer prettier option --plugin= instead of --parser= for prettier-ruby and prettier-svelte
2. Use standard local rust/rustfmt install for test setup instead of tarball (no longer available)
   • install locally, change permissions to make the install visible to all users, and then symlink to the install dir and config in the global /etc/bash.bashrc so local test user will picks them up.
3. Change filename to download for nixfmt (now includes OS/arch)
   • There was initially no binary available when nixfmt was updated, but the devs there were kind enough to provide one: https://github.com/serokell/nixfmt/issues/139