Add support for `file-system-info' in Tramp

Add support for `file-system-info' in Tramp

* lisp/net/tramp.el (tramp-file-name-for-operation):
Add `file-system-info'.

* lisp/net/tramp-adb.el (tramp-adb-handle-file-system-info): New defun.
(tramp-adb-file-name-handler-alist): Use it.

* lisp/net/tramp-gvfs.el (tramp-gvfs-file-system-attributes)
(tramp-gvfs-file-system-attributes-regexp): New defconst.
(tramp-gvfs-handle-file-system-info): New defun.
(tramp-gvfs-file-name-handler-alist): Use it.
(tramp-gvfs-get-directory-attributes): Fix property name.
(tramp-gvfs-get-root-attributes): Support also file system attributes.

* lisp/net/tramp-sh.el (tramp-sh-handle-file-system-info): New defun.
(tramp-sh-file-name-handler-alist): Use it.
(tramp-sh-handle-insert-directory): Insert size information.
(tramp-get-remote-df): New defun.

* lisp/net/tramp-smb.el (tramp-smb-handle-file-system-info): New defun.
(tramp-smb-file-name-handler-alist): Use it.
(tramp-smb-handle-insert-directory): Insert size information.

* test/lisp/net/tramp-tests.el (tramp-test37-file-system-info):
New test.
(tramp-test38-asynchronous-requests)
(tramp-test39-recursive-load, tramp-test40-remote-load-path)
(tramp-test41-unload): Rename.