Improve docs of functions/variables related to 'display-buffer'

Improve docs of functions/variables related to 'display-buffer'

* lisp/window.el (display-buffer, pop-to-buffer-same-window)
(display-buffer-same-window, display-buffer-in-side-window)
(same-window-p, display-buffer-overriding-action)
(display-buffer-base-action)
(display-buffer--same-window-action)
(display-buffer--other-frame-action)
(with-current-buffer-window, with-displayed-buffer-window)
(display-buffer-alist, display-buffer-assq-regexp)
(display-buffer-other-frame): Clarify and improve the doc
strings.  (Bug#32798)