kunit/fortify: Add memcpy() tests

kunit/fortify: Add memcpy() tests

Add fortify tests for memcpy() and memmove(). This can use a similar
method to the fortify_panic() replacement, only we can do it for what
was the WARN_ONCE(), which can be redefined.

Since this is primarily testing the fortify behaviors of the memcpy()
and memmove() defenses, the tests for memcpy() and memmove() are
identical.

Link: https://lore.kernel.org/r/20240429194342.2421639-3-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>