wic/direct/kparser: ensure fsuuid for vfat and msdos align with format

vfat/msdos filesystem should have fsuuid in format 0xYYYYYYYY where "0x"
in front follow with 8 hexadecimal number in uppercase. In wic, when using
custom fsuuid for vfat/msdos partition in wks, it is able to set the value
in any length, with or without leading "0x". This can cause fsuuid
missaligned when fstab updates, fstab expect exactly 10 character
fsuuid for vfat/msdos partition and all in uppercase.

if custom fsuuid for vfat/msdos is set, check the length and format,
error if it exceed the format size. Amend it so it is align with format
0xYYYYYYYY. This is done before image create and fstab update to ensure the
fsuuid are same in all followup process. if custom fsuuid length less than
expected, fill in "0".

[YOCTO #14161]

Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit d9686ae5)
Signed-off-by: Steve Sakoman <steve@sakoman.com>