Cleanup also recentf files in Tramp

Cleanup also recentf files in Tramp

* doc/misc/tramp.texi (Cleanup remote connections): Mention also
recentf cache.

* lisp/net/tramp-cmds.el (tramp-cleanup-connection)
(tramp-cleanup-all-connections): Call `tramp-recentf-cleanup'.

* lisp/net/tramp-integration.el: New package.

* lisp/net/tramp.el (tramp-rfn-eshadow-overlay)
(tramp-rfn-eshadow-setup-minibuffer)
(tramp-rfn-eshadow-update-overlay-regexp)
(tramp-rfn-eshadow-update-overlay):
(tramp-eshell-directory-change): Move to tramp-integration.el