bootctl: show more information about boot entry state in list

bootctl: show more information about boot entry state in list

Let's improve display of boot entries and show what type they have (i.e.
boot loader spec type 1, or type 2, or auto-discovered or reported by
boot loader), and in particular mark entries the boot loader discovered
but we can't find (i.e. that likely vanished, or possibly couldn't be
found due to a misconfiguration) and that the boot loader didn't find
but we see (which are new, or possibly also the result of
misconfiguraiton).

This is supposed to be a replacement for #22161, but instead of hiding
vanished entries, highlights them, which I think is more appropriate for
a low-level tool such bootctl.

Replaces: #22161 #22398