Kill our own hand-rolled (and somewhat flawed) devpath_str in favor of
the recently added efi_devpath_str in libefi. This gives us much
better names at the expense of not being able to debug on EFI 1.2
machines (since the UEFI protocol efi_devpath_str depends on was added
in UEFI 2.0). However, this isn't the first thing that requires newer
than EFI 1.2, so it's quite possible that this doesn't change the
universe of machines we can EFI boot from. This will now give us the
full UEFI path, even for devices we don't yet know about. More
importantly, it gives us the full HD(...) part of the path, which is
sufficient by itself to locate disks that follow the rules (dd one
disk (but not partition) to another still needs the rest of the path
to disambiguate, but that isn't following the rules that require every
GPT table to have globally unique GUIDs for every partion).
This also has the side effect of shrinking boot1.efi by ~3k.
Sponsored by: Netflix
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