Add tests for `kill-whole-line' (bug#65734)

Add tests for `kill-whole-line' (bug#65734)

* test/lisp/simple-tests.el (simple-test-point-tag):
(simple-test-mark-tag):
(simple-test--set-buffer-text-point-mark):
(simple-test--get-buffer-text-point-mark): Add helper functions used by
the tests.
(kill-whole-line-invisible):
(kill-whole-line-read-only):
(kill-whole-line-after-other-kill):
(kill-whole-line-buffer-boundaries):
(kill-whole-line-line-boundaries): Add tests for `kill-whole-line'.

(cherry picked from commit aa10d0c5ac1a4d706b8562671f2a22a82f9e733b)