[Feature]: Add visual measuring tools, like Figma

还没有人认领这个 Issue。

Validating layouts is not a simple task, usually we need to open Figma, measure the distance between widgets there, and try to see if it matches in the app. Currently there are many hacky ways to do it:

1. Take a screenshot of the app, overlay it on Figma/Photohop, and use rulers to check alignment and sizes.
2.Take a screenshot of the app, overlay it on Figma/Photohop, and use opacity to blend the desired outcome with the screenshot, and see where they differ.
3. Take a screenshot of the app and use any tool that can count pixels to see if the values match what you want.

All of this takes time and it's cumbersome.

Currently we can see the size of a widget in the widget tree view, but that's it.

It would be really cool if the DevTools could introduce a tool like this:

Where we can use the mouse and keyboard to activate different kinds of measurements, from one widget to the next. I suggest you play around with Figma, pressing Alt/Option while you select and hover over components, to see how it helps to measure distances between widgets.

Obviously this will be more complicated in a real device, but for emulators it could be really useful.

从 DevTools 的 widget 树视图开始，目前该视图会显示 widget 大小，并审查 issue 中提出的 Figma 风格交互。完成标准是：已定义在模拟器中使用鼠标和键盘测量 widget 之间距离的范围和交互细节。

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