Don't mutate constants in tests

Don't mutate constants in tests

* test/lisp/emacs-lisp/cl-macs-tests.el
(cl-macs-test--symbol-macrolet):
* test/lisp/emacs-lisp/cl-print-tests.el
(cl-print-tests-ellipsis-circular):
* test/lisp/emacs-lisp/eieio-tests/eieio-test-persist.el
(eieio-test-persist-interior-lists):
* test/lisp/textmodes/reftex-tests.el (reftex-all-used-citation-keys):
* test/src/xdisp-tests.el (xdisp-tests--minibuffer-resizing):
* test/src/fns-tests.el (test-vector-delete):
Mutate created objects, not constants.

* test/lisp/emacs-lisp/subr-x-tests.el
(subr-x-test-add-display-text-property): Mutate a created string, and
compare using `equal-including-properties` without which the test was
rather meaningless.

* test/lisp/net/tramp-archive-tests.el
(tramp-archive-test16-directory-files): Don't mutate.