Merge topic 'sphinx-cref'

302f5171d8 Utilities/Sphinx: Add 'cref' role
bc77ddb90c Utilities/Sphinx: Factor out part of CMakeXRefRole

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !8313