legend分页回调 #3855

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

如果图例有两页，第一页两行，第二页一行，点击下一页后图例位置没有变，然后点击图例更新图形后再点击上一页，图例和图形或者缩略轴就会出现重合，点击完翻页后重新render图形legend位置就能实时更新了；

What does the proposed API look like?

图例配置pageNavigator中添加图个回调函数，updateNavigation后回调；

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