bug#70897: Guix system hangs on boot with LUKS root partition

[Kaelyn]

Hi Ludo' and others,

I recently updated my systems after finally finding 
https://issues.guix.gnu.org/70051 and seeing the issue I was having with 
booting with a non-root LUKS partition configured had been fixed. After 
updating to a commit past these two:

  49f82fca41 mapped-devices: luks: Specify modules needed at the top-level.
  6062339156 mapped-devices: <mapped-device-type> can specify modules to import.

I am now seeing a different error, which I am pretty sure is related to the 
module import changes in 49f82fca41. The error I get is about an unknown symbol 
"system*/tty" when the initramfs tries to prompt for a password to unlock the 
LUKS partition containing the root filesystem. I don't know how the module 
plumbing of Shepherd and the generated initramfs work, but I suspect the fix 
for Shepherd opening LUKS partition broke the import of system*/tty in the 
initramfs (for example, at the early REPL that booting my latest system 
generation ends up at, system*/tty is undefined initially, but after evaluating 
"(use-modules (gnu build file-systems))" system*/tty resolves to a procedure as 
exected--so the module is at least present in the initramfs). I have 
encountered this error with two different systems, and I believe the 
reproduction is simply trying to open a LUKS device without a keyfile so that a 
password prompt is necessary.

Cheers,
Kaelyn