Allow scoping CodeLens links to folders

In DevTools, it'd be nice to commit this scoped to `integration_tests`:

```js
{
	"name": "Debug (release mode)",
	"type": "dart",
	"request": "launch",
	"template": "run-test",
	"env": {
		"WEBDEV_RELEASE": true,
	}
}
```

Currently it would cause the links to show up in non-integration test files too.