Merge topic 'doc-target_link_libraries' into release-4.0

1d07da0912 Help: Clarify context of target_link_libraries pre-4.0 behavior documentation
b7dc28cb8c Help: Drop target_link_libraries redundant prose on debug/optimized keywords
b4bac3018f Help: Drop target_link_libraries mention of CMP0003 and CMP0004
639eee1a0c Help: Call out target_link_libraries legacy signatures earlier

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Yegor Yefremov <yegorslists@googlemail.com>
Merge-request: !10326