vim-patch:9.1.1802: 'nowrap' in a modeline may hide malicious code (#35946)

Problem:  'nowrap' in a modeline may hide malicious code.
Solution: Forcibly use '>' as 'listchars' "extends" if 'nowrap' was set
          from a modeline (zeertzjq).

Manual `:setlocal nowrap` disables this behavior.  There is a separate
problem with `:set nowrap` that also applies to some other options.

related: vim/vim#18214
related: vim/vim#18399
closes: vim/vim#18425

9d5208a931

Cherry-pick some test_modeline.vim changes from patches 9.0.{0363,0626}.

src/nvim/options.lua

@@ -10811,6 +10811,11 @@ local options = {
         <	See 'sidescroll', 'listchars' and |wrap-off|.
         This option can't be set from a |modeline| when the 'diff' option is
         on.
+        If 'nowrap' was set from a |modeline| or in the |sandbox|, '>' is used
+        as the |lcs-extends| character regardless of the value of the 'list'
+        and 'listchars' options.  This is to prevent malicious code outside
+        the viewport from going unnoticed.  Use `:setlocal nowrap` manually
+        afterwards to disable this behavior.
       ]=],
       full_name = 'wrap',
       redraw = { 'current_window' },