Merge topic 'doc-4.2-relnotes'

5e9722866a Help: Update Sphinx versionadded directives for 4.2 release
5c7e90d954 Help: Organize and revise 4.2 release notes
ec28123cb4 Help: Consolidate 4.2 release notes

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !11271