ext4_utils: allow specifying HEH filenames encryption

Make the ext4_utils changes needed to support specifying aes-256-heh
filenames encryption.  The previous mode, aes-256-cts, remains supported
as well.

The file /data/unencrypted/mode is updated to have the syntax
contents_encryption_mode[:filenames_encryption_mode] instead of just
contents_encryption_mode.  This is consistent with the new fstab syntax.

Bug: 34712722
Change-Id: Ia40f589ed46dd008ab2c65d28995b574c45bbac0
3 files changed