The existing symLinkTarget() always resolves the symlink target to an
absolute path; readSymLink() provides access to the relative path when
that is how the symlink references its target.
[ChangeLog][QtCore][QFileInfo] Added readSymLink() to read the symlink's
raw target, without resolving to an absolute path.
Fixes: QTBUG-96761
Change-Id: I360e55f1a3bdb00e2966229ea8de78cf29a29417
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>