Rename test file to end with _test so it runs on the bots (#21438)

* Rename test file

* Fix detection to work regardless of whether there are other devices

On Windows we get one message, but on Mac we get another (because of the Simulator always being available).

packages/flutter_tools/test/integration/flutter_run.dart → packages/flutter_tools/test/integration/flutter_run_test.dart

@@ -38,7 +38,10 @@ void main() {
 
       expect(_proc.stdout, isNot(contains('flutter has exited unexpectedly')));
       expect(_proc.stderr, isNot(contains('flutter has exited unexpectedly')));
-      expect(_proc.stderr, contains('Unable to locate a development'));
+      if (!_proc.stderr.toString().contains('Unable to locate a development')
+        && !_proc.stdout.toString().contains('No devices found with name or id matching')) {
+          fail("'flutter run -d invalid-device-id' did not produce the expected error");
+        }
     });
   }, timeout: const Timeout.factor(6));
 }