Add systemd drop-in to wait for snapd seeding completion before starting the
display manager. This improves the user experience as users now wait in
Plymouth for the installer to finish being seeded, instead of in GDM with only
the wallpaper visible. When GDM starts, the installer launches with minimal
delay.
When developping and using snapd from edge on cross-team efforts like
TPM/FDE, allow snapd to reexec to the snap version unconditionnaly,
on live system.
.
This is commented so that the future revert to stable include it and
we don’t forget to readd that next time this kind of effort is needed.
