Tramp code cleanup

Tramp code cleanup

* lisp/net/tramp.el (tramp-get-default-directory)
(tramp-get-buffer-string): New defsubsts.
(tramp-message, tramp-error-with-buffer)
(tramp-file-name-for-operation, tramp-command-completion-p)
(tramp-action-login, tramp-action-yesno, tramp-action-yn)
(tramp-action-terminal, tramp-action-confirm-message)
(tramp-wait-for-regexp, tramp-call-process)
(tramp-call-process-region, tramp-read-passwd):
* lisp/net/tramp-cmds.el (tramp-list-remote-buffers)
(tramp-reporter-dump-variable):
* lisp/net/tramp-gvfs.el (tramp-gvfs-monitor-process-filter):
* lisp/net/tramp-sh.el (tramp-sh-handle-insert-directory)
(tramp-sh-handle-process-file, tramp-sh-handle-write-region)
(tramp-sh-gio-monitor-process-filter):
* lisp/net/tramp-smb.el (tramp-smb-action-set-acl):
* lisp/net/tramp-sudoedit.el
(tramp-sudoedit-handle-file-name-all-completions):
* test/lisp/net/tramp-tests.el (tramp--test-instrument-test-case)
(tramp-test32-shell-command): Use them.