Extend tramp-tests

Extend tramp-tests

* test/lisp/net/tramp-tests.el (tramp--test-deftest-with-stat)
(tramp--test-deftest-with-perl, tramp--test-deftest-with-ls):
New defmacros.
(tramp-test18-file-attributes-with-stat)
(tramp-test18-file-attributes-with-perl)
(tramp-test18-file-attributes-with-ls)
(tramp-test19-directory-files-and-attributes-with-stat)
(tramp-test19-directory-files-and-attributes-with-perl)
(tramp-test19-directory-files-and-attributes-with-ls): New tests.
(tramp-test21-file-links): Delete also `tmp-name2'.
(tramp--test-deftest-direct-async-process): Rename from
`tramp--test--deftest-direct-async-process'.  Remove DOCSTRING.
Adapt callees.
(tramp--test-special-characters): Remove.  Move body to ...
(tramp-test41-special-characters): ... here.
(tramp--test-utf8): Remove.  Move body to ...
(tramp-test42-utf8): ... here.
(tramp-test41-special-characters-with-stat)
(tramp-test41-special-characters-with-perl)
(tramp-test41-special-characters-with-ls)
(tramp-test42-utf8-with-stat)
(tramp-test42-utf8-with-perl)
(tramp-test42-utf8-with-ls): Rewrite, using the new macros.