建议java api提供获取父元素节点、子元素节点及兄弟元素节点的方法

* **Macaca Version**:

* **Macaca Doctor Logs**:

* **Operate System**: Mac

* **Programming Language**: Java

1、 ios 的原生app 根据xpath，class不好定位元素，并且很多控件的name是没有值的；
2、有些父元素的子元素个数、名称是变化，需要通过父元素去动态获取子元素的个数，从而来定位元素

Start by locating the Java API used for iOS native-app element lookup and review how XPath, class, and name selectors are exposed. Clarify the expected parent, child-count/name, and sibling behavior, then add tests for dynamically discovering child elements and verify the requested API behavior.

Written by the indexing model from the issue text.