kunit: fix up const mis-match in many assert functions

kunit: fix up const mis-match in many assert functions

In many kunit assert functions a const pointer is passed to
container_of() and out pops a non-const pointer, which really isn't the
correct thing to do at all.  Fix this up by correctly marking the
casted-to pointer as const to preserve the marking.

Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Rae Moar <raemoar63@gmail.com>
Cc: linux-kselftest@vger.kernel.org
Cc: kunit-dev@googlegroups.com
Reviewed-by: David Gow <davidgow@google.com>
Link: https://patch.msgid.link/2025121746-result-staleness-5a68@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>