Prefer oddp/evenp to free-coding them in tests

Prefer oddp/evenp to free-coding them in tests

* test/lisp/emacs-lisp/bindat-tests.el (bindat-test--sint):
* test/lisp/emacs-lisp/seq-tests.el (test-seq-drop-while)
(test-seq-take-while, test-seq-filter, test-seq-remove)
(test-seq-count, test-seq-some, test-seq-find, test-seq-every-p)
(test-seq-group-by):
* test/lisp/eshell/em-pred-tests.el (eshell-with-file-attributes-from-name):
* test/lisp/filenotify-tests.el (file-notify-test07-many-events)
(file-notify-test09-watched-file-in-watched-dir):
* test/src/floatfns-tests.el (bignum-expt, bignum-round):
* test/src/undo-tests.el (undo-test4): Prefer oddp/evenp to free-coding
them.

(cherry picked from commit 5ce746c3b0fa3a0b73796182960ff06cf3f31473)