Prevent loading tramp-archive when it cannot be used

Prevent loading tramp-archive when it cannot be used

* lisp/files.el (locate-dominating-file): Check, that FILE is
a directory when traversing the tree.

* lisp/net/tramp-archive.el (tramp-archive-enabled): New defvar.
(tramp-archive-file-name-regexp): Protect against errors.
(tramp-archive-file-name-handler)
(tramp-register-archive-file-name-handler): Use it.
(all) Call `tramp-register-archive-file-name-handler'.

* lisp/net/tramp.el (tramp-register-file-name-handlers):
Use `tramp-archive-enabled'.

* test/lisp/net/tramp-archive-tests.el (all):
Use `tramp-archive-enabled' instead of `tramp-gvfs-enabled'.
(tramp-archive--test-emacs27-p): New defun.
(tramp-archive-test42-auto-load): Skip for older Emacsen.
(tramp-archive-test42-delay-load): Skip for older Emacsen.
Test also behavior when `tramp-archive-enabled' is nil.