repart: Restore early generation of fstab/crypttab

repart: Restore early generation of fstab/crypttab

Commit 15b1c33 ("repart: Generate fstab and crypttab late") moved
fstab/crypttab generation to the late stage but this introduced a regression:
it may be necessary to include fstab and crypttab into the generated partition
(e.g. with CopyFiles=). This is incompatible with 'fixate-volume-key' option as
it is impossible to capture LUKS volume key before it gets created but all the
rest should work fine.

Generate crypttab twice: early and late to capture possible changes. There's no
need to do the same for fstab for now, so keep the status quo.