Merge topic 'release-3.20-cleanups' into release-3.20

7c147b21 Help: Add Ninja Multi-Config and make generator types into links
5039ca11 Help: Convert output directory variable mentions to cross-references
1a7e51b9 Help: Cleanup wording and links in 3.20 release notes
d1683032 CPackIFW: Improve warning and docs for show page list option
7ed7db88 CPackIFW: Fix cppcheck warnings

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !5810