Options to automatically stop the Emacs server

Options to automatically stop the Emacs server

* doc/emacs/misc.texi (Emacs Server): Document the new function.
Also mention that an Emacs server can be started with emacsclient.

* etc/NEWS: Describe the new function (bug#51377).
* lisp/server.el (server-stop-automatically): New function.
(server-stop-automatically): New auxiliary variable.
(server-stop-automatically--maybe-kill-emacs)
(server-stop-automatically--handle-delete-frame): New auxiliary
functions.
(server-save-buffers-kill-terminal): Call the new auxiliary
function when necessary.