Support for archive file names

Support for archive file names

* doc/misc/tramp.texi (Top, Usage): Add entry "Archive file names".
(History): Mention archive file names.
(GVFS based methods): Mentio "http" and "https" methods.
(Archive file names): New node.
(Frequently Asked Questions): Add Emacs 27 as supported version.

* etc/NEWS: Mention tramp-archive.el.

* lisp/net/tramp.el (tramp-run-real-handler)
(tramp-register-file-name-handlers)
(tramp-register-file-name-handlers, tramp-unload-file-name-handlers):
Add `tramp-archive-file-name-handler'.
(tramp-handle-file-name-completion): Do not insist in Tramp
file names.

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

* lisp/net/tramp-cache.el (tramp-dump-connection-properties): Check for
"archive" method.

* lisp/net/tramp-cmds.el (tramp-cleanup-all-connections): Cleanup also
local copies of archives.

* lisp/net/tramp-compat.el (tramp-compat-use-url-tramp-p): New defconst.

* lisp/net/tramp-gvfs.el (tramp-gvfs-methods): Add "http" and "https".
(tramp-gvfs-gio-mapping): Add "gvfs-mount".
(tramp-gvfs-handler-mounted-unmounted)
(tramp-gvfs-connection-mounted-p, tramp-gvfs-mount-spec):
Handle "uri" and "http".
(tramp-gvfs-unmount): New defun.

* test/lisp/net/tramp-archive-tests.el: New package.