Eliminates support for Dart 1 in flutter_tools, and drops our Dart 1
benchmarks. All commands now run in Dart 1 mode only.
Eliminates --preview-dart-2 / --no-preview-dart-2 support.
* Remove '\n' from terminal input.
* Use trim instead of replaceAll
* Add unit test
* Cleanup the test
* Fixed lint
* Style adjustments
* Forgotten @override
* Revert "Forgotten @override"
Accidently added extra files.
This reverts commit 0aba24fc8e.
* Just @override change