Merge topic 'mutable-find-package-stack-alt'

b3873b8272 cmFindPackageStack: Allow controlled mutation
f2bdc2176f cmStack: New, mutable stack class

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !10978