Add some retry around launching browsers

[natebosch]

test/pkgs/test/lib/src/runner/browser/browser_manager.dart

Lines 129 to 133 in d6329d6

	return completer.future.timeout(Duration(seconds: 30), onTimeout: () {
	browser.close();
	throw ApplicationException(
	'Timed out waiting for ${runtime.name} to connect.');
	});

We seem to hit timeouts much more often on github actions.

[natebosch]

@grouma - does package:browser_launcher already have retry?

#1156

[grouma]

I don't think so: https://github.com/dart-lang/browser_launcher/blob/master/lib/src/chrome.dart