Improve Tramp tests

Improve Tramp tests

* lisp/net/tramp-smb.el (tramp-smb-handle-copy-file):
Handle compressed files.

* lisp/net/tramp.el (tramp-skeleton-write-region):
Handle encrypted VISIT file.
(tramp-get-process-attributes): Add backward compatibility.

* test/lisp/net/tramp-tests.el (with-connection-local-variables):
Declare.
(auto-save-file-name-transforms): Don't declare.
(ert-resource-directory-format)
(ert-resource-directory-trim-left-regexp)
(ert-resource-directory-trim-right-regexp, ert-resource-directory)
(ert-resource-file): Define if they don't exist.
(tramp-test10-write-region-file-precious-flag)
(tramp-test10-write-region-other-file-name-handler)
(tramp-test31-interrupt-process, tramp-test31-signal-process)
(tramp--test-async-shell-command)
(tramp-test34-connection-local-variables)
(tramp-test39-make-lock-file-name)
(tramp-test39-detect-external-change): Extend tests.