Deprecate `StringUtils.isEmpty(Object)` and replace remaining usage (e.g. with `ObjectUtils.isEmpty`)

[sabi0]

With static imports code like this looks perfectly fine:

        List<String> data = ...

        if (isEmpty(data)) {

But if the import has StringUtils.isEmpty the condition above will not work correctly for empty List introducing a hidden, difficult to spot bug.

If you are really keen on keeping this method it would be better to rename it to isEmptyString to at least make the error more obvious. (I believe this name also matches the method intention better than generic isEmpty.)

But with the #17710 in place I do not think StringUtils.isEmpty(Object) is still needed. And should probably be deprecated and eventually removed.