`pacinstall` does not handle virtual packages

When a target is only provided by other targets, `pactrans` can not locate it. For example:
```
❯ sudo pacman -S i3
:: There are 5 members in group i3:
:: Repository community
   1) i3-gaps  2) i3-wm  3) i3blocks  4) i3lock  5) i3status

Enter a selection (default=all):
```
```
❯ sudo pacinstall i3
error: could not locate package 'i3'
```