Show better error messages when configured browser is not installed

This is my launch config: ```json { "name": "Monaco Editor Playground", "type": "chrome", "request": "launch", "url": "https://microsoft.github.io/monaco-editor/playground.html?sourceLanguages=http%3A%2F%2Flocalhost%3A5002%2Fout%2Famd", "preLaunchTask": "Launch Http Server", }, ``` [When a user launches it without having chrome installed](https://github.com/microsoft/vscode/issues/174870#issuecomment-1439187546_), they get this error: <img width="429" alt="image" src="https://user-images.githubusercontent.com/25044782/220477910-29a4cefa-b035-48a4-9e35-8b838ca7c35d.png"> > Unable to launch browser: "Unable to find an installation of the browser on your system. Try installing it, or providing an absolute path to the browser in the "runtimeExecutable" in your launch.json I think it might be a better UX if the error better explains what is wrong. This could look like this: > Cannot start debug session: The configured browser "chrome" does not seem to be installed. Try installing it, or providing an absolute path to the browser in the "runtimeExecutable" in your launch.json * This explains that this error prevents debugging the application * It mentions which browser it is missing