Add constants for shell command output buffer names

Add constants for shell command output buffer names

Buffers `*Shell Command Output*' and `*Async Shell Command*'
have been around since a long time; used across several libraries,
they are de facto output buffers for shell commands.

* lisp/simple.el (shell-command-buffer-name)
(shell-command-buffer-name-async): New variables.
* lisp/dired-aux.el
* lisp/gnus/gnus-sum.el
* lisp/gnus/gnus-win.el
* lisp/ibuf-ext.el
* lisp/net/tramp.el: Use them.

* etc/NEWS (Changes in Emacs 28.1): Announce this change.

* doc/emacs/misc.texi (Single Shell)
* doc/misc/tramp.texi (Remote processes):
Update manual (bug#39138).