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/state.c

@@ -135,9 +135,9 @@ void state_handle_k_event(void)
 }
 
 /// Return true if in the current mode we need to use virtual.
-bool virtual_active(void)
+bool virtual_active(win_T *wp)
 {
-  unsigned cur_ve_flags = get_ve_flags();
+  unsigned cur_ve_flags = get_ve_flags(wp);
 
   // While an operator is being executed we return "virtual_op", because
   // VIsual_active has already been reset, thus we can't check for "block"