Make full disk encryption optional

Created by: ollieparanoid

For performance reasons, the full disk encryption should become optional.

Required changes:

• pmbootstrap install:
  • Add a --no-fde switch (or something like that)
  • Always assign a partition label to the postmarketOS root partition (this is something we should do anyway)
• postmarketos-mkinitfs:
  • Instead of searching for a cryptsetup partition, find the postmarketOS root partition by device label
  • When it was found, check whether it is encrypted or not. If it isn't, directly boot from it