hibernate-resume: automatically decrypt dissected swap if told so via autoSwap

hibernate-resume: automatically decrypt dissected swap if told so via autoSwap

With the addition of /dev/disk/by-designator/ along with
ID_DISSECT_PART_DESIGNATOR attr, it is now trivial to tell
whether the swap device we hibernated into is the "auto" one.
Hence use that bit of info and generate cryptsetup unit
in hibernate-resume-generator if that's the case.

Ideally, gpt-auto should really just handle swap already
in initrd, which would save us a myriad of trouble and
the system behaves more consistently. But I don't see that
happening anytime soon. This is the second best option
we have I reckon.

Closes #27247 (#35328, #37330)