- this supports custom kernel users to continue not having to fastboot reflash vbmeta with --disable-verity and --disable-verification, now that Magisk 24303+ no longer patches avb out of the fstab on-the-fly at boot time
- checks for an avb option in the fstab entry for the current partition
- if found, it checks if verity or verification is disabled on the top-level vbmeta, and if so, appends a hashtree and FEC data to the partition and updates the hashtree descriptor in the vbmeta partition referenced in the avb option