ext2 is not supported for placing persistent files

[Jozsef Gyurusi]

If live-booting the ubuntu iso with persistence using persistent files, then when persistent files are searched in scripts/casper-helpers/find_cow_device, ext2 and other non-journalling filesystems are not supported, except vfat.
This makes impossible to create a persistent file larger than 4GB since the files are found only if they put on a partition using vfat.

To reproduce the issue, put casper-rw (or writable) or home-rw file on a partition using an ext2 filesystem to the root folder.
Then boot the ubuntu iso in persistent mode with proper persistent-path parameter like 'persistent-path=/'. During boot the persistent files will not be found. However, if the filesystem is vfat, the persistent boot will be successful.

The fix for casper_1.501 to add only the ext2 support:

--- a/scripts/casper-helpers
+++ b/scripts/casper-helpers
@@ -223,7 +223,7 @@ find_cow_device() {
             # will cause data loss when a live CD is booted on a system
             # where filesystems are in use by hibernated operating systems.
             case "$(get_fstype ${devname})" in
- vfat)
+ vfat|ext2)
                     :;;
                 *)
                     continue;;

The ubuntu release I used: 22.04.01 LTS.