Handle remote system processes

Handle remote system processes

* doc/lispref/files.texi (Magic File Names):
Add list-system-processes and process-attributes.

* doc/lispref/processes.texi (System Processes): Document changes
in list-system-processes and process-attributes.

* doc/misc/tramp.texi (Customizing Completion): Use @ftable.
(Remote processes): Document changes in list-system-processes and
process-attributes.

* etc/NEWS: Document changes in proced, list-system-processes and
process-attributes.

* lisp/proced.el (proced-show-remote-processes): New defcustom.
(proced-remote-directory): Remove.
(proced-filter-alist): Use it.
(proced-user-name): New defun.
(proced-available): Set it to t.
(proced-mode): Adapt docstring.
(proced): Adapt docstring.  Acknowledge prefix argument.
(proced-format): Change initialization of `standard-attributes'.
(proced-send-signal, proced-renice): Adapt docstring.  Remove
special handling of prefix argument.

* lisp/net/tramp-adb.el (tramp-adb-file-name-handler-alist):
* lisp/net/tramp-archive.el (tramp-archive-file-name-handler-alist):
* lisp/net/tramp-crypt.el (tramp-crypt-file-name-handler-alist):
* lisp/net/tramp-gvfs.el (tramp-gvfs-file-name-handler-alist):
* lisp/net/tramp-rclone.el (tramp-rclone-file-name-handler-alist):
* lisp/net/tramp-sh.el (tramp-sh-file-name-handler-alist):
* lisp/net/tramp-smb.el (tramp-smb-file-name-handler-alist):
* lisp/net/tramp-sshfs.el (tramp-sshfs-file-name-handler-alist):
* lisp/net/tramp-sudoedit.el (tramp-sudoedit-file-name-handler-alist):
Add 'list-system-processes' and `process-attributes'.

* lisp/net/tramp-integration.el (files-x): Require `files-x'.
(tramp-bsd-process-attributes-ps-args)
(tramp-bsd-process-attributes-ps-format)
(tramp-connection-local-bsd-ps-variables)
(tramp-busybox-process-attributes-ps-args)
(tramp-busybox-process-attributes-ps-format)
(tramp-connection-local-busybox-ps-variables):
* lisp/net/tramp-adb.el (tramp-adb-connection-local-default-ps-variables):
New defconsts.  Add them to connection-local variables.

* lisp/net/tramp.el (tramp-file-name-for-operation):
Add 'list-system-processes' and `process-attributes'.
(tramp-process-attributes-ps-args)
(tramp-process-attributes-ps-format): New defconsts.
(tramp-ps-time, tramp-get-process-attributes)
(tramp-handle-list-system-processes)
(tramp-handle-process-attributes): New defuns.

* src/process.c (Flist_system_processes, Fprocess_attributes):
Support remote system processes.
(Qlist_system_processes, Qprocess_attributes): Declare symbols.