xfs: Symbolic links support

- Necessary hooks for reading symlinks are implemented

- Added support for local symlinks

- Added support for extent based symlinks

- This patch completes #17791

Change-Id: If6847974562b21f751097df357326f4643eff757
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5621
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>