xfs: update the Short-Attributes Class.

Update: OnDisk format and manage endianness for the ShortAttribute Class.A separate private function to Swap endianness is implemented inside the Class

Change-Id: I348d6c0ac128fe56d63a16e4f10ff90708c6a7a4
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7582
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Haiku-Format: Haiku-format Bot <no-reply+haikuformatbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

xfs: Enable -Werror, fix all warnings

Define a dedicated OnDiskData structure for each on-disk structure. This
must match the on-disk layout, except for endianness, which is handled
by _SwapEndian methods. These structure are "plain old data" so we can
use offsetof on them. They are wrapped in an easier to use C++ API.

This resolves a lot of problems with the previous code: warnings caused
by the use of offsetof as well as a much simpler instanciation of the
objects from on-disk data.

Also fixed another problem with UUIDs, where the UUIDs were handled by
pointers in a lot of place where it was not necessary. Use references
instead. The V4 structures which don't have an UUID will return a "null"
(zero-filled) one.

Change-Id: Ifb2bf6ab94906ca50410dd3446d3566615392ca2
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6021
Reviewed-by: Raghav Sharma <raghavself28@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

xfs: extended attributes necessary hooks and shortform attributes support

- Implemented all necessary hooks for extended attributes in kernel_interface.cpp

- Implemented an abstract class attribute which will act as an interface between all forms of extended attributes in xfs

- An attempt to read shortform extended attributes

Change-Id: Icff9329b790f9fcfc0b078f61059795af9d9e486
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5570
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>