Avoid leaving artifacts when the system caret is used on w32

Avoid leaving artifacts when the system caret is used on w32

* src/xdisp.c (try_window_reusing_current_matrix, try_window_id):
* src/dispnew.c (scrolling_window) [HAVE_NTGUI]: If
w32-use-visible-system-caret is non-nil, disallow scrolling the
display are in scroll_run_hook.  This avoids copying traces of the
caret, about which Emacs knows nothing, and thus considers those
pixels show the default background.  (Bug#39188)
(gui_update_window_end): Block input only around part of the code,
as we did before this code was extracted from backend-specific
implementations.

* src/w32term.c (w32_update_window_begin, w32_update_window_end):
Only hide/show the caret when redisplaying the window where the
caret is shown.