Split ways on crossing points

To fix mapping errors like this where the sidewalk stops but the road is not split, it would be great to have a simple split option in the editor.
The parking lane editor https://zlant.github.io/parking-lanes/#18.19/52.747057/13.240385 had a similar feature where one could select a scissors icon and then all intersections showed the icon so I could click it to split the way.

However, there needs to be some checks to handle relations, which ATM every editor has to implement themselves. See also https://github.com/rapideditor/rapid-sdk/issues/165
The code from zlant and iD and MapComplete should have checks that can be reused.

Examples: Route relations can just be copied. But the order are an issue. But other relations like turn restrictions should not be copied.

The easiest is to just disallow splitting when there are relations.

该 issue 提到了 zlant 的 parking lane editor、iD 和 MapComplete 中已有的实现。首先检查这些编辑器如何处理在交叉路口拆分 way，尤其是它们对 relation 的检查。在代码库中查看当前编辑器的 way 拆分逻辑，并确定在哪里添加剪刀图标 UI 以及 relation 处理检查。'Done' 表示用户可以选择拆分工具并在交叉路口拆分 way，同时适当地处理 route relation 和 turn restriction。

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