Merge topic 'cpack-rpm-zstd-compression'

fab5c030ad CPack/RPM: Add zstd compression support
a25be17bc4 CPack/RPM: emit error on invalid CPACK_RPM_COMPRESSION_TYPE
7e21412f47 CPack/RPM: fix whitespace alignment prior to editing
e0b73a32c1 Help: Clarify using CPACK_THREADS as default

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !9632