when displaying flutter framework errors, we should detect hyperlinks to code

For example, here's some of the text of a 'flutter.error' error message:

```
User-created ancestor of the error-causing widget was:
Container file:///Users/devoncarew/projects/sergiandreplace/flutter_planets_tutorial/lib/ui/common/plannet_summary.dart:51:35
```

We should detect source file references and convert them into links. In IntelliJ, those would link to the source for the user's app. For DevTools, we might want to link to the source in the debugger view? Another option would be to open the file in any associated IDE (also connected to the app via the service protocol). Or, we could link to the devtools debugger view, and in that view, have an option to open a file in a connected IDE, if there was one.

I think the user will want to jump to the source, inspect the problem a bit, and then make a small change to a file, and reload. We'll want to support that effectively in DevTools.

Beginne damit nachzuverfolgen, wie DevTools flutter.error-Text anzeigt und wie Quellpositionen über das Service Protocol bereitgestellt werden. Vergleiche die Verknüpfung mit der Debugger-Ansicht mit dem Öffnen von Dateien in einer verbundenen IDE; abgeschlossen ist die Aufgabe, wenn Quellverweise wie file:///...:51:35 zu nutzbaren Links mit einem eindeutigen Ziel werden.

Vom Indexierungsmodell aus dem Issue-Text verfasst.