Some minor changes to Tramp, do not merge with master

Some minor changes to Tramp, do not merge with master

* lisp/net/tramp.el (tramp-handle-directory-files)
(tramp-handle-directory-files-and-attributes):
* lisp/net/tramp-adb.el
(tramp-adb-handle-directory-files-and-attributes):
* lisp/net/tramp-rclone.el (tramp-rclone-handle-directory-files):
* lisp/net/tramp-sh.el (tramp-sh-handle-directory-files-and-attributes):
* lisp/net/tramp-smb.el (tramp-smb-handle-directory-files): Add _COUNT.
Make the functions forward compatible.

* lisp/net/tramp-gvfs.el (tramp-gvfs-enabled):
Increase `max-specpdl-size' temporarily.

* test/lisp/net/tramp-tests.el (tramp--test-share-p): New defun.
(tramp-test05-expand-file-name-relative): Use it.