fix(api/buffer): fix handling of viewport of non-current buffer

A lot of functions in move.c only worked for curwin, alternatively
took a `wp` arg but still only work if that happens to be curwin.

Refactor those that are needed for update_topline(wp) to work
for any window.

fixes #27723
fixes #27720

src/nvim/optionstr.c

@@ -2479,9 +2479,8 @@ const char *did_set_virtualedit(optset_T *args)
     } else if (strcmp(ve, args->os_oldval.string.data) != 0) {
       // Recompute cursor position in case the new 've' setting
       // changes something.
-      validate_virtcol_win(win);
-      // XXX: this only works when win == curwin
-      coladvance(win->w_virtcol);
+      validate_virtcol(win);
+      coladvance(win, win->w_virtcol);
     }
   }
   return NULL;