patch 9.2.0919: screen: the wrong array is copied into ScreenCols on a resize

patch 9.2.0919: screen: the wrong array is copied into ScreenCols on a resize

Problem:  When the screen is resized without clearing, screenalloc() copies
          ScreenAttrs[] into the new ScreenCols[] instead of using
          ScreenCols[], so the virtual columns are replaced by attribute
          values.  Since colnr_T is twice the size of sattr_T it also
          reads twice the intended number of bytes.
Solution: Copy from ScreenCols[].

closes: #20961

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>