Control the preference to always show the DevTools pages on startup from DevTools

VSCode has custom UX to let users opt into always running the inspector. The problem is it is surfaced before users have actually used the inspector so they aren't sure whether it is valuable. We should surface UX inside the embedded devtools to opt in and out of always showing the embedded devtools.

"You have used the inspector a lot, would you like to always launch it when you open DevTools?"

"You haven't interacted with the inspector in N days, would you like to stop seeing it when you debug a flutter app?"

DevTools server should be driving whether the inspector pages are automatically shown on startup from IDEs. That way DevTools can surface the option to opt in and out of always showing the embedded DevTools on startup.

Downside: weird for an IDE setting to be tracked in DevTools rather than the individual IDES. We could mitigate this if we wanted to get fancy by surfacing UX for this in the IntelliJ and VSCode plugin settings as well as DevTools but I'm not sure the complexity would be worth it.

Bonus points:
Also offer the option of always showing DevTools on startup for command line users. I'd personally like this option but I'm biased.

先从嵌入式 DevTools 启动时的 DevTools 服务器行为入手，然后将 VSCode 和 IntelliJ 插件设置与命令行启动路径进行比较。定义 DevTools 应如何根据 inspector 的使用情况让用户选择启用或退出，并记录 IDE 设置是否也需要相应的 UX。完成标准是：启动偏好设置在所请求的各个入口点上都能一致地工作。

由索引模型根据 Issue 内容生成。