Move dired tests using ls emulation to different files

Move dired tests using ls emulation to different files

Suggested in:
https://lists.gnu.org/archive/html/emacs-devel/2017-08/msg00018.html
* test/lisp/dired-tests.el (dired-test-bug27693)
(dired-test-bug27762, dired-test-bug27817)
(dired-test-bug27631, dired-test-bug27843): Delete those
parts requiring either ls-lisp or eshell-ls.

* test/lisp/ls-lisp-tests.el (ls-lisp-test-bug27762)
(ls-lisp-test-bug27631, ls-lisp-test-bug27693):
Add all dired tests using ls-lisp here.

* test/lisp/eshell/em-ls-tests.el (em-ls-test-bug27631)
(em-ls-test-bug27817, em-ls-test-bug27843): New test file.  Add
all dired tests using eshell-ls here.