Simplify debug

Hi VS Code PM here 👋

I just followed [this tutorial](https://docs.microsoft.com/en-us/dotnet/core/tutorials/with-visual-studio-code) to setup a simple C# app and to debug it. Here's my feedback on what I think we could improve:

1. C# should consider contributing to the Editor title area menu, such that a Play button would appear in the Editor Title area. [Example how to do this](https://github.com/microsoft/vscode-mock-debug/blob/main/package.json#L80)
2. You ask the user via a notification that "things are missing to run and debug..." and your intention is to automatically create a `launch.json`. This helps the flow, but is out of the context, since user did not even trigger debugging. Instead of this I suggest that your extension simply provides a dynamic `resolveDebugConfiguartion` that will provide a launch configuration on the fly. [Example](https://github.com/microsoft/vscode-mock-debug/blob/main/src/activateMockDebug.ts#L161). That way you can generate the config when it is needed, and in memory. Alternatively: if you really want to write into `launch.json` you should do it when the user starts debugging I think.
3. If the user does not see the notification it is impossible to debug since you are not resolving debug configurations on the fly
4. If I have a purple no folder VS Code it is impossible to debug a simple C# file
5. Consider contributing to an Empty debug view to make C# debug setup easier (C++ does this for example)

I would love if we could improve this experience, since we see in user studies that users want a confirmation that VS Code can do C#, and providing an easy way to run and debug simple C# files would be great for this.

Let me know if I can help somehow. I am also open to a quick 30 min meeting where we can discuss about the new cool VS Code debug features that C# could potentially adopt and you could let us know what are your biggest ask for the VS Code debugger.

fyi @gregg-miskelly @weinand