Move scrolling commands from simple.el to window.el

Move scrolling commands from simple.el to window.el
because their primitives are implemented in window.c.

* simple.el (scroll-error-top-bottom)
(scroll-up-command, scroll-down-command, scroll-up-line)
(scroll-down-line, scroll-other-window-down)
(beginning-of-buffer-other-window, end-of-buffer-other-window):
* window.el (scroll-error-top-bottom)
(scroll-up-command, scroll-down-command, scroll-up-line)
(scroll-down-line, scroll-other-window-down)
(beginning-of-buffer-other-window, end-of-buffer-other-window):
Move from simple.el to window.el because their primitives are
implemented in window.c.