Implement shape constraints for `Cross` (#14156)

* Implement shape constraints for `Cross`

This fix implements shape constrainsts for `Cross`, as
was specified in the TODO:
```
    // * Both inputs have the same shape.
    // * Input rank >= 1.
    // * input_shape[-1] == 3.
```

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add unit test for shape constraint and inference for `Cross`

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>