Add a view where I can see code snippets for every frame in the stack

Observatory has a really cool UI where you can expand and collapse the code snippet around each frame in the stack. This makes it easier to understand where you are without jumping across files and lines in a view limited to a single file.

Can we replicate this?

首先检查 Observatory 针对每个 frame 的可展开代码片段视图，并将其与 DevTools 当前的堆栈视图进行比较。在定位相关的堆栈视图入口点之前，先定义预期的交互方式和范围；完成的标准是每个 frame 都能在不离开堆栈视图的情况下展开或折叠其周围的代码片段。

由索引模型根据 Issue 内容生成。