Adapt Tramp password prompts for sudo-like methods

Adapt Tramp password prompts for sudo-like methods

* doc/misc/tramp.texi (Password handling): Explain entries for
doas, sudo and sudoedit.

* etc/NEWS (Tramp): Document changed password prompts.

* lisp/net/tramp-sh.el (tramp-methods) <sudo, doas>:
Add `tramp-password-previous-hop'.
(tramp-maybe-open-connection): Modify `previous-hop' if needed.

* lisp/net/tramp-sudoedit.el (tramp-methods) <sudoedit>:
Add `tramp-password-previous-hop'.
(tramp-sudoedit-null-hop): New defconst.
(tramp-sudoedit-send-command): Use it.

* lisp/net/tramp.el (tramp-methods): Adapt docstring.
(tramp-null-hop): New defconst.
(tramp-get-remote-null-device): Use it.