Merge topic 'doc-3.31-relnotes'

aa6bbc3135 Help: Update Sphinx versionadded directives for 3.31 release
738cf491d4 Help: Organize and revise 3.31 release notes
fae66f4751 Help: Consolidate 3.31 release notes

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !9878