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: minimised disk seeks for node xattrs

- Made GetNext() function in Node Attributes efficient by reducing disk seeks to number of Node entries

Change-Id: I4e2bf8fb1898676c30eca2c6d6f39dc1999ae2f8
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5612
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

xfs: make common lower bound function for calculating index of Hash

Change-Id: I5e902031b0e2a1051a7f96ab94dca0dba0ca9112
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5698
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

xfs: leaf xattrs

- Implemented leaf based extended attributes on-disk headers

- Both version 4 and version 5 attributes can be read now

- Implemented all leaf headers check to ensure metadata integrity

Change-Id: Ifc3f2e433e991776bb02d1d38f621d5bd1554a4e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5600
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>