tune2fs: allow disabling casefold feature

tune2fs: allow disabling casefold feature

Casefold can be safely disabled if there are no directories with +F
attribute ( EXT4_CASEFOLD_FL ). This checks all inodes for that flag and in
case there isn't any, it disables casefold FS feature. When FS has
directories with +F attributes, user could convert these directories,
probably by mounting FS and executing some script or by doing it
manually. Afterwards, it would be possible to disable casefold FS flag
via tune2fs.

Link: https://lore.kernel.org/r/20220708122658.17907-1-slava@bacher09.org
Signed-off-by: Slava Bacherikov <slava@bacher09.org>
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>