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: Node xattrs

- Implemented node based extended attributes support

- Both Versions of xfs node based extended attributes can be read now

Change-Id: I2d2915029435e7722cf463b1e2b5579b361dd592
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5606
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>